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I realize that this is a very basic question, but I can't find an answer anywhere.
I'm computing regression coefficients using either the normal equations or QR decomposition. How can I compute standard errors for each coefficient? I usually think of standard errors as being computed as:
$SE_\bar{x}\ = \frac{\sigma_{... |
Suppose we are using Simulated Annealing (SA) to minimize a cost function $L:\mathbb{R} \to \mathbb{R}$. Here is my algorithm:
(1). Randomly choose a $x_0 \in \mathbb{R}$. Set $x=x_0$ and $T=T_0$.
for k=1:m
(2). Propose a new point $x_{new}$ by sampling $N(x, \sigma^2)$, where
$\sigma$ is a constant.
(3). If $L(x_{new... |
Are there any straightforward methods of transforming ordinal level data into interval level (just as there are for doing it the other way round)? And performable in Excel or SPSS?
Having the data, say:
10 questions on the ordinal level (say 0-5 scale, where 0="not at all", 5="all the time"),
I want to tranform them s... |
What methods would you recommend for testing whether a variable Y is the weighted sum of n, not necessarily independent, variables? Only m < n of these variables are known.
The problem is easy if the variables are independent. (In my setting their co-variance is close to zero).
|
I know that we can use Spearman rho to measure the correlation between numerical variables. But how to measure correlation between categorical variables?
|
I have near about 50 files(each file corresponds to a patient) with 4 columns -
chromosome start.position stop.pos value
First 3 columns in all 50 files are same and fourth column is value which is different (or can be same for some) for all patients. Basically this value corresponds to copy number (str... |
For homework I have been given a 20-dimensional input $x \in \mathbb{R}^{20}$, many of which are suspected to be irrelevant. I tried using L1-norm Lasso regularization to uncover which dimensions contribute to the output:
$$L(\beta) = \sum_{i=1}^n (y_i - \phi(x_i)^T \cdot \beta)^2 + \lambda \sum_{j = 1}^k l(\beta_j)$$... |
Given any number of clusters, is it possible to estimate the Sum of Squares Error (SSE) for the Clusters after adding noise to the clustering?
The type of noise generated will be supplied as a parameter. Any method(s) must be able to cater for Gaussian and Uniform noise.
|
What is the meaning and effect of %in% in a model formula?
It is apparently used for nesting of one variable into another in a variety of analysis (manova, anova, regressions) in a few published articles.
From ?formula, b%in%a is a:b, so why use %in%?
How is a:b nesting?
I am probably mistaken, but my understanding is ... |
I'm interested in the simple algorithm for particles filter given here. It seems very simple but I have no idea on how to do it practically. Any idea on how to implement it (just to better understand how it works) ?
Edit:
This is a great simple example that explain how it works. I've tried to implement it in C++: see ... |
I am building ruby on rails (ActiveRecord) horse racing application. One of the features that I would like to include in the application is the ability to identify meaningful "Angles". For example, given the following facts:
Horse A has raced 50 times and has 30 Wins
Jockey B was riding Horse A for 25 of Horse As 30... |
I am using AICc for small sample sizes to compare 8 a priori models (including null model). I fitted my models using a GLMM due to the nested nature of my data and defined the family as 'poisson' based on a visual inspection of the error structure from my residual vs fitted values plot.
After running my analysis using ... |
I've read that using log scales when charting/graphing is appropriate in certain circumstances, like the y-axis in a time series chart. However, I've not been able to find a definitive explanation as to why that's the case, or when else it would be appropriate.
Please keep in mind, I'm not a statistician so I may be m... |
Please suggest a data entry tool (if one exists) for a single large sparse table.
Something like...
row x, checkbox list of 300 columns, check 5 that pertain, enter data for those 5.
row x+1, same checkbox, check different 14 that pertain, enter data for those 14.
row x+2, checkbox does not contain column, add column t... |
As we all know, profile likelihood is an effective method for the estimation of conditional parametric model. But I still don't know exactly why it works. Profile likelihood was thoroughly studied by Severini and Wong (1992).
By profile likelihood, can we obtain an unbiased, asymptotically efficient estimator for the p... |
I have written a program which generates random data. If the program is working correctly, that data should follow a specific, known probability distribution. I would like to run the program, do some calculations on the result, and come up with a p-value.
Before anybody else says it: I understand that hypothesis testin... |
I am trying to apply dimensionality reduction on an a set of images (~3000 pixels) using Matlab's Dimensionality Reduction toolbox. However, I know very little about dimension reduction. So I tried several functions by trial and error. PCA returned a matrix with complex numbers, and the others froze MATLAB. Can I get s... |
In the Lasso L1 regularization, from where comes the value of the variable $k$ in the second part of the function? Why isn't it $n$, too?
$$L(\beta) = \sum_{i=1}^n (y_i - \phi(x_i)^T \cdot \beta)^2 + \lambda \sum_{j = 1}^k l(\beta_j)$$
$\beta$ is the parameter vector, $y$ the output vector and $x$ the input vector.
|
Suppose a time-serie like this on the left-top corner with weekend and daily fluctuations. This time-series need differencing due to the rising ACF (bottom-left) and portmanteau tests' p -values too small, the weekend must be differenced away. Now I want to differentiate away the weekend-fluctuation in R, how to do tha... |
I understand that ,usually, time-series studies do not aim to provide a causal explanation of anything but rather aim to forecast. In which case it does make sense that most time series studies aren't concerned with omitted variable bias.
However, I've come across a time series study that seeks to explain Soviet defen... |
Forgive me if I've missed something rather obvious.
I'm a physicist with what is essentially a (histogram) distribution centered about a mean value that approximates to a Normal distribution. The important value to me is the standard deviation of this Gaussian random variable. How would I go about trying to find the e... |
I have a dataset for around 40k firms over fiscal years 1950-2011 with about 430k firm-years. If I'm not mistaken I have panel data.
I created a unique identifier ticn for each firm. Years are indicated by fyear. For now my variables of interest are yearly sales sale, yearly advertising xad, and yearly R&D expenses xr... |
I need to determine if a single number "fits" with a group of numbers. All the numbers will be percentages, so we'll use decimals.
For example:
The group is: 0.1, 0.25, 0.3, 0.4, 0.9 and we'll test against two single numbers: $y_1$ = 0.2 and $y_2$ = 0.8
The group is all low numbers, except for the one outlier, 0.9.
So ... |
I have a categorical fixed effect with 3 levels that I'm trying to enter into an LME.
a = lmer(Reaction ~ ContinuousEffect * CategoricalEffect + (1|Subject) + (1|StrengthOfStimulus))
StrengthOfStimulus is a numerical variable that's being used as a random effect, along with Subject.
Now, for some reason, when I run th... |
I'm trying to write a program that automatically groups similarities between vectors. The vectors are comprised of point coordinates.
For example (assuming X, Y, and Z are numbers):
Data Set 1: [1, 8, X1, X2, 6, X3, X4, 8, 5, 4, 9, 4, Y1, Y2, Y3, Y4, Y5, 1, 5, 7]
Data Set 2: [X1, X2, X3, X4, 6, 3, 5, 4, 3, 6, Y1, Y2, ... |
Let $X = (X_1, \ldots, X_p) \sim F$ be a multivariate random vector. We have n iid observations from F, $\{x_i\}_{i=1}^n$. Let $\hat r_{ab}$ be the empirical estimate of the partial correlation between $X_a$ and $X_b$ given all the other components of F.
What results are known for $P[|\hat r_{ab} - r_{ab}| > t] \leq f... |
Given an infinite sequence of values, selected at random (with replacement) from a set of N values, I choose some value X from the set of values. Then, starting from the first occurrence of X in the sequence, I count the number of values between each subsequent occurrence of X, giving a new sequence. What is the mean... |
For a recent project, I used multiple linear regression to model data. I attempted to choose between my initial full model and a reduced model by performing a partial F-test. The models used were the following:
Full model: $\hat{Y}$ = $B_0$ + $B_1$$x_1$ + $B_2$$x_2$ + $B_3$$x_3$
Reduced Model: $\hat{Y}$ = $B_0$ + $B_2$... |
I am new to ARIMA modelling. I understand most of the basic concepts, and I've read a lot of topics about ARIMA on this site.
At present I am pretty comfortable with analysing ACF and PACF graphs, checking for seasonality and creating model from my data.
Next step I want to deal with outliers and periodic pulses in m... |
I have a series of timestamps, and I would like to know what's the maximum hourly rate of the event that these timestamps represent. You can generalize this to any units. I'm looking for a window (interval) of a certain size that contains most of these values. The obvious approach is to divide the set by this interval ... |
I've been reading the Wikipedia articles about various statistical tests, and trying to code up programs that perform them. However, the article on the Kolmogorov-Smirnov test is rather unclear to me. Can somebody explain, in simple language, how I would write a program that takes a list of real numbers and a CDF, and ... |
I am new to SVM. I would like to use SVM to segment/cluster/classify a road image into two distinct regions i.e. drivable region and non-drivable region. Unfortunately, I do not have any images where the regions are already labeled.
I really don't know how to go about this i.e. specifying the training set.
Will weka be... |
I'm doing some analysis of Bureau of Labor Statistics data on wages earned by men and women, and I'm trying to determine which of the two methods I've used is the better estimate of the gender wage gap.
The first compares the median weekly earnings of all women employed full-time (669 USD) against the median weekly ear... |
What sort of mean can I use in calculating the average of the deviations of actuals from a forecast, which are in percent. The data look(s) like this:
-0.26
-0.21
-0.9
1.56
1.88
For example, the last unit above beat the forecast by 1.88%. My intuition was geometric (based on this question), but I am not sure how to to... |
I have been tasked with trying to modify our current "index" which basically takes 4 observations per person and calculates a score based on what they achieve. Here is how the score is created (all variables are ordinal in nature, higher scores representing more desirable outcomes):
Variable A - gets a score of 1 to ... |
I have a question concerning the use of the kwallis2 test in Stata. If looking at the multiple comparison output, I receive a probability and (NS) or (S).
What does the probability there mean and to what does the program compare this value to reach the outcome significant or not? I suppose that the standard 5% signific... |
There are three bandwidth selector functions programmed in the ks package: Hpi, Hscv and Hpi.kfe, what is the difference between them?
And what is the difference between a plug-in and a smoothed cross validation bandwidth selector?
|
I'm involved in a census at our condo association. We may, for logistics reasons, survey 1/4 of the population per quarter so that we have surveyed everyone by the end of the year, but let's assume we survey everyone at once.
A year later, we survey again. Since we're attempting to cover 100% of the population each yea... |
I have a data set (21 binned values) which I have fitted to a Gaussian with IDL ($\mu=3.825$, $\sigma =0.0377$). I have tried to find the $\chi^2$, getting $21.14$ for $20$ d.f.. Here my understanding is a little shakey; I think this means I can be 60% confident that the distribution is normal (please correct me if I'm... |
I'm new to data mining and I'm trying to train a decision tree against a data set which is highly unbalanced. However, I'm having problems with poor predictive accuracy.
The data consists of students studying courses, and the class variable is the course status which has two values - Withdrawn or Current.
Age
Ethnicit... |
I remember being taught that correlation is a test of association and regression is test of relationship.
In addition, I remember learning that association means that no assumption is made on which variable is independent and which variable is dependent, whereas relationship implies such a distinction.
My question: Are... |
Some people are playing a game online. Every time a person plays, a new game board is generated randomly. On generation of a new board, the player can also choose a special weapon. (The choice of weapon does not affect the board generation.)
Over time, observed data are like this:
player weapon win
3 5 0 #... |
I'm wanting to generate random connected directed acyclic graphs, and am wondering if there is a way of populating an adjacency matrix in R which would represent the aforementioned.
Something similar to this would be nice (that is done with Mathematica): https://mathematica.stackexchange.com/q/608
Thanks.
|
When I perform cluster analysis in SAS, the SAS log sometimes return a warning something like this:
WARNING: Ties for minimum distance between clusters have been
detected at 4 level(s) in the cluster history.
Depends on the clustering methods (all hierarchical clustering methods) I choose, the number... |
Sorry, if the title is confusing. not native speaker here.
I ran a survey study which had 15 7-point likert scale questions. Each question is ask people to judge how creativity an object in the picture. I received 153 responses in total.
What I try to understand is whether those people who answered the survey did a si... |
A non-profit has donors with monthly commitments, which you can think of as subscriptions. What is the best way to show for each month new acquisitions, cancels, and net growth? The relationship is
net growth = new acquisitions - cancels
The same time of chart could be appropriate for net profit (business) or net in... |
Say I have a simple machine learning problem like a classification. With some benchmarks in vision or audio recognition, I, as a human, are a very good classifier. I therefore have an intuition on how good a classifier can get.
But with lots of data one point is that I do not know how good the classifier I train is pos... |
Using Bayes' theorem, $P(A|B) = \frac{P(B|A)P(A)}{P(B)}$
wouldn't this just be the percentage of $A$ in $B$ if $A$ is a subset of $B$?
If A is a subset of B:
$$P(B|A) = 1,$$
$$P(A|B) = \frac{P(A)}{P(B)}$$
Therefore Bayes theorem becomes $\frac{P(A)}{P(B)}$ if $A$ is a subset of $B$.
So you don't really need to use Baye... |
In this paper, the talented researcher Cosma Shalizi argues that to fully accept a subjective Bayesian view, one must also accept an unphysical result that the arrow of time (given by the flow of entropy) should actually go backwards. This is mainly an attempt to argue against the maximum entropy / fully subjective Bay... |
Suppose I have $k$ 'experts', from whom I would like to elicit a prior distribution on some variable $X$. I would like to motivate them with real money. The idea is to elicit the priors, observe $n$ realizations of the random variable $X$, then divvy up some predetermined 'purse' among the experts based on how well the... |
I am currently doing my MBA and I am attempting to find out what variables affect new student intake at the university which I am working at. My model is based on the 7Ps of the marketing mix (Product, Place, Price, Promotion, People, Process and Physical Evidence) and non-marketing mix factors (such as influence of pe... |
I was wondering if anyone had experience using the mice function, as described in mice: Multivariate Imputation by Chained Equations in R (JSS 2011 45(3))? I have a dataset with a number of variables, each with varying degrees of missing data.
My primary question is: say I use Bayesian linear regression to impute miss... |
Here are four different sets of numbers:
A = {95.47, 87.90, 99.00}
B = {79.2, 75.3, 66.3}
C = {38.4, 40.4, 32.8}
D = {1.8, 1.2, 1.1}
Using a two-sample t-test without assuming equal variances, I compare B, C, and D to A and get the following p-values:
0.015827 (A vs B)
0.000283 (A vs C)
0.001190 (A vs D)
I find ... |
Emerson, J. D. (1991) Graphical Display as an Aid to Analysis, in Fundamentals of Exploratory Analysis of Variance (eds D. C. Hoaglin, F. Mosteller and J. W. Tukey), John Wiley & Sons, Inc., Hoboken, NJ, USA. doi: 10.1002/9780470316832.ch8
There describes side-by-side plots of effects and residuals...
I think it's a ni... |
In a multivariate context, that is with at least X or Y being a random vector, are there formulae or theorems that link (even remotely) the forward and inverse regression, $\text{E}(X|Y)$ and $\text{E}(Y|X)$ ?
Or alternatively $\text{E}(X_i|Y)$ and $\text{E}(Y|X_i)$, where $X_i$ is a given component of $X$.
Similarly, ... |
I used mvpart to produce a classification tree (response variables concerning travel behaviour, explain variables are socio-demographic). In the output I can see the averages of the travel behaviour variables for the different segments formed by the tree. Is there a way to test if these differences are statistical sign... |
For a university course, a friend of mine had to test whether there is a relation between two ordinal variables. These variables were opinion about the European Union (positive, neutral, negative) and whether people felt being (a) citizen of their country, (b) primarily citizen of their country, but also European, (c) ... |
I'm trying to specify a model in JAGS/rjags with one between subjects factor (a, with two levels - Y, N) interacting with one repeated measures continuous variable x plus subject varying slopes and intercepts that correlate. I can specify this model simply enough with the lmer function:
lmer(y ~ a + x + a:x + (1 + a | ... |
I am interested in finding the relation between two (possibly multi dimensional) time series $x_{1:T}$ and $y_{1:T}$. I wonder how I can do that with a linear dynamical system/Kalman filter.
My approach would be sth like estimating the parameters $\theta$ with EM for the joint probability $p(x_{1:T}, y_{1:T}, h_{1:T})$... |
I recently read about a package, which I believe had a name like "tabstat" or "tablestats" which produced a really useful plot of univariate distributions of multiple variables for large datasets. I believe this package was developed by google, but am not sure. I can't seem to find it anywhere (tabstat on google retu... |
First, I want to clarify this is a very basic question. I'm new using R (and programming in general).
I have a data.frame with 3 columns:
block, average condition 1, average condition 2.
The blocks run from 1 to 9 and the average are response times averaged across subjects.
What I want to do is to plot both average... |
I am using the estimated county-level poverty measure from the Small Area Income and Poverty Estimates (SAIPE) as the dependent variable in a regression analysis. This value is itself the result of a model and comes complete with upper and lower 90% confidence interval bounds. To be clear, each of my 3000+ observations... |
I am doing regression task and the response variables in my dataset have a skewed distribution. Say, for the sake of simplicity, that I have a model Y~X and Y(response variable) is in [1,5] but there are many more values in the [4,5] range than the [1,2] range. As a result a majority predictor that predicts 4.5 for Y ... |
I have a manuscript on a bootstrap method for testing hypotheses of one mean, and I would like to send it for publication, but I have a moral dilemma. I have signed on to the protest against Elsevier for their unethical business practices, and reading up on the whole issue really made me question the ethics of other fo... |
I'm looking for difficult Bayesian inference problems to test out different Monte Carlo sampling methods. I've mostly been looking at Hamiltonian Monte Carlo based algorithms and in particular, I've been using the trick of using the hessian at the Maximum A Posteriori point for the mass matrix.
What are some practical ... |
Suppose a grant program allows city administrators to allocate the grant across three mutually exclusive categories 1, 2, 3.
City administrators are surveyed to elicit their preferred allocations. A response by administrator i is a triplet R_i = (p1, p2, p3), where by definition: 0 <= pi <= 100 for all i in {1,2,3} ... |
I am interested in the definition of quartile that is usually used when you're in basic statistics. I have a Stat 101 type book and it just gives an intuitive definition. "About one quarter of the data falls on or below the first quartile..." But, it gives an example where it calculates Q1, Q2, and Q3 for the set of... |
I have two sets of data, and I want to know if the second set is sufficiently different from the first to be considered different.
More specifically, I have a sample set A from a number of pixels in the vicinity of point X in an image, and another sample B of pixels in the vicinity of point Y in the same image.
I want ... |
This may be a basic question, but I was wondering why an $R$ value in a regression model can simply be squared to give a figure of explained variance?
I understand that $R$ coefficient can give the strength of a relationship, but I don't understand how simply squaring this value gives a measure of explained variance.
... |
I am doing a sample size calculation for a survey and am using the formula found at the bottom of this page: http://www.raosoft.com/samplesize.html
In the formula, r is 'the fraction of responses that you are interested'. What is this exactly? I thought it would be the percentage of the population I want to look at, bu... |
Let's say I have a $n \times m$ centered data matrix $A$ with SVD $A = U \Sigma V^{T}$.
For example, $m=50$ columns (measurements) that are spectra with $n=100$ different frequencies. The matrix is centered so the rows of the matrix have their mean subtracted. This is for interpreting the left singular vectors as princ... |
I have a question:
Is it true that $$P((-z \leq Z \leq z) = \alpha = 2(P(Z \leq z) = \alpha/2)$$ by symmetry?
So you really only need to find one value of $z$?
|
What is the expected length of a streak of heads or tails when flipping a coin? What distribution is this?
I'm pretty sure the answer is 2. But I don't know what distributions it is..
I did the following R code:
l=10000
longest.stk = avg.stk = numeric(l)
for(i in 1:l){
x=sample(0:1, 1000, repl=T)
r = rle(x)
longest.st... |
I have two spectra of the same astronomical object. The essential question is this: How can I calculate the relative shift between these spectra and get an accurate error estimate on that shift?
Some more details if you are still with me. Each spectrum will be an array with an x value (wavelength), y value (flux), and ... |
Say clustering was performed. My concern is to understand what characterizes certain cluster. Which variables differ most for a certain cluster? Are there any methods for performing such kind of analysis?
For example, say I have 50 variables and 10 clusters. The desired result would sound like: for a cluster 1 variable... |
Imagine I wish to see the effect of some treatment on the correlation between two groups of variables, which I measure with Spearman's rank correlation coefficient.
Treatment A gives a Spearman's rank of 0.4, 0.44, 0.43 for my 3 replicates.
Treatment B gives a Spearman's rank of 0.48, 0.45, 0.46 for my 3 replicates
Tre... |
Following my previous question, I used Dixon test for outliers with the help of Michael Chernick answer. So now I have pvalues for say 10 numbers (basically 10 patients). But I have around 50k pvalues and I want to know that which patient has an outlier. Example-
chr start.position stop.pos pvalue pat1 ... |
If you fit a linear model or a mixed model there are different types of codings available to transform a categorical or nominal varibale into a number of variables for which paramaters are estimated, such as dummy conding (the R default) and effects coding.
I heard that effects coding (sometimes called deviation or con... |
I have a dataset X which has 10 dimensions, 4 of which are discrete values.
In fact, those 4 discrete variables are ordinal, i.e. a higher value implies a higher/better semantic.
2 of these discrete variables are categorical in the sense that for each of these variables, the distance e.g. from 11 to 12 is not the same ... |
What is the minimum number of observations to be considered in order to determine long range dependency?
I'm trying to estimate Hurst parameter using R/S method. I've used SELFIS as well as R.
Logically, since we are interested in long range dependency, we should have enough observations. SELFIS requires at least 64 va... |
I am trying to run a regression from a 11300x21500 observation matrix (where there are 11300 observations and 21500 independent variables). However, when I try to implement the usual $(X^T X)^{-1}$ formula in C++, I can't even initialize the observation matrix $X$ due to memory limitations (The application closes itse... |
In the definition of jointly typical sets (in "Elements of Information Theory", ch. 7.6, p. 195), we use
$$-\frac{1}{n} \log{p(x^n)}$$ as the empirical entropy of an $n$-sequence with $p(x^n) = \prod_{i=1}^{n}{p(x_i)}$. I never came across this terminology before. It is not defined explicitly anywhere according to the... |
Is there a method for constructing decision trees that takes account of structured/hierarchical/multilevel predictors, that would allow me to impose domain knowledge or constraints on interactions for example?
|
In contrast to the many threads on this site that recommend Dixon's and Grubb's tests, the author of one answer, at this thread, contends that "Really, these have been discredited long ago" and advocates 2 other methods. I don't feel qualified to sort out these arguments, but I would like to ask whether there is any c... |
First, I want to know how to analyze a dataset to discover its pattern.
And second, how can I select the best kernel function for classifying a dataset?
|
As you probably know, the CDFs for many widely-used distributions are difficult, if not impossible, to express in closed form without the use of special functions
The normal distribution uses $\mathrm{erf}$.
Student's $t$-distribution requires the incomplete beta function or the Euler gamma function
The $\chi^2$ dist... |
What would you guys suggest as a good introduction book to small area estimation?
|
Let's say I am using a logistic model to predict whether it rains (yes or no) based on the high temperature and have collected data for the past 100 days. Let's say that it rains 30/100 days. Furthermore, let's say that 70/100 days the temperature is actually 50 degrees. So there were only 30/100 days where the tempera... |
I have a project in which I am looking at the correlation betwen fortnightly income and the amount saved each fortnight by low income workers.
I am reporting the effect size and the confidence interval. One of my results is as follows: r (214) = 0.34, p < 001, 95% CI [0.22, 0.45]
I know it is accepted that a narrow con... |
I've got one independent variable and two dependent variables. As a concrete example, consider the independent variable to be browser (categorical, what Web browser a visitor to a Web site uses) and the dependent variables to be visitors (number of visitors) and enrollers (number of visitors who sign up for a newslette... |
I'm using guassian process regression to do some modeling. One issue I'm encountering is feature selection for some of my models, which often have many relevant features. I'm not sure what the best way to reduce the # of features is. I understand that some covariance functions in GPR use automatic relevance detection, ... |
If $X$ and $Y$ are independent random variables, then the variance
of the product $XY$ is given by
$
\mathbb{V}\left(XY\right)=\left\{ \mathbb{E}\left(X\right)\right\} ^{2}\mathbb{V}\left(Y\right)+\left\{ \mathbb{E}\left(Y\right)\right\} ^{2}\mathbb{V}\left(X\right)+\mathbb{V}\left(X\right)\mathbb{V}\left(Y\right)
$
... |
Cross-posted from math; let me know if you need me to wait there for a bit before posting here
I have a set of datapoints in $\mathbb{R}^3$ (integer or real values of $X$, $Y$ and $Z$, for, say. 30 points).
I need to do a least squares regression for linearity. If the data set is linear, I need to see if it is close t... |
Suppose we have the following data set:
Men Women
Dieting 10 30
Non-dieting 5 60
If I run the Fisher exact test in R then what does alternative = greater (or less) imply? For example:
mat = matrix(c(10,5,30,60), 2,2)
fisher.test(mat, alternative="greater")
I get the p-v... |
I know the ratio of 2 normally distributed random variables is a cauchy distribution...which, of course, has no variance.
But, if I have $X$ and $Y=|X|$ and take this ratio:
$Z=X/Y$, is it possible to find the variance of the ratio of the normal distribution to the half normal?
Edit: (More details)
I am missing someth... |
@JeromyAnglim, thanks for your answer to "How to determine the sample size needed for repeated measurement ANOVA". My question: Is there a formula to estimate the minimum number of time points required for repeated measurements when we do a clinical trial? I know that there's a formula to estimate the sample size when... |
Based on the responses from the question How to draw a side-by-side plot mentioned in "Graphical Display as an Aid to Analysis", I am considering implementing the function myself. The problem is that I don't know how to utilize the result of aov() function. I have to see how many factors there are, the names of facto... |
What is the distribution of the following monomial?
$$X^a \cdot Y^b$$
where $X$ and $Y$ are normal random variables and $a$ and $b$ are natural numbers.
For example, when $X \sim N(0,1)$, $a=2$, and $b=0$ it is a Chi-squared distribution, which has a variance of 2.
What if we have $n$ independent variables $X_1, X_2, \... |
I have learnt the definition of AIC for parametric model. But, what I want to know is that is there a semi-parametric version of AIC?
Have you heard about it? And if you know, please show me a link, so I can have a look.
|
Following my question here, I am also looking at the difference between males and females and I have conducted linear regression in a general linear model setup for this purpose.
My effect size for this part of the project is $\eta^2$ (which is 0.25).
$\eta^2$ is equivalent to $R^2$ (which is the appeal for me in this... |
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