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At first I thought the order didn’t matter, but then I read about the gram-schmidt orthogonalization process for calculating multiple regression coefficients, and now I’m having second thoughts.
According to the gram-schmidt process, the later an explanatory variable is indexed among the other variables, the smaller it... |
Both bootstrap and jackknife methods can be used to estimate bias and standard error of an estimate and mechanisms of both resampling methods are not huge different: sampling with replacement vs. leave out one observation at a time. However, jackknife is not as popular as bootstrap in research and practice.
Is there an... |
Plotting a glm binomial model is reasonably simple with the predict function. I'm having trouble creating a similar plot for a glmer model; predict doesn't work:
id <- factor(rep(1:20, 3))
age <- rep(sample(20:50, 20, replace=T), 3)
age <- age + c(rep(0, 20), rep(3, 20), rep(6, 20))
score <- rbinom(60, 15, 1-a... |
I'm a part of a volunteer organization that organizes a bunch of events. For each event, members need to submit an application in order to attend the event. A lot of people want to go to these events and we only have a limited number of spots available, so the selection process is usually pretty competitive. The app... |
I'm working with Gaussian process regression. Currently I start testing different covariance functions and compositions to see what type of data they could describe best. I made an own implementation in Java.
My problem: Most of the covariance functions I use result in a singular covariance matrix which is not inverti... |
I want to use Discriminant Analysis between two non normal populations in R. Can anybody tell me the name of the R function to do so?
Could also anybody tell me how accurate my results will be if I violate the normality assumption?
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I'm working with a dataset of combined continuous and categorical data, and I'm constructing a regression model based on both types of data simultaneously, using dummy variables. The model will look something like this:
$y = \alpha + \beta_1 x_1 + \beta_2 x_2$
where, for example, $x_1 \in [0,1]$ is continuous, and $x_2... |
I have a data set with gene expression levels measured for three different treatments, and for each treatment we have three biological replicates. Treatments are: Control, 24h at $4$°C, and 24h at $-3$°C. This analysis was carried out on two genotypes.
CTRL1 CTRL2 CTRL3 4°C_1 4°C_2 4°C_3 -3°C_1 -... |
I have looked at different web tools for calculating confidence intervals for effect size like Cohen's d for within-subject design. My experience from this survey tells me that there are different ways to estimate within SD because results I got differs on both effect size and confidence intervals. They usually use cor... |
R linear regression seems to fail if my predictor variance is very small, but nonzero:
> reg = lm(V1~V2,data)
> summary(reg)
Call:
lm(formula = V1 ~ V2, data = data)
Residuals:
Min 1Q Median 3Q Max
-15.968 -4.898 1.627 5.218 8.468
Coefficients: (1 not defined because of singularities)
... |
I've designed and programmed an ANN, So now I need to do an analysis about results, I've seen some examples where they do graphics about surface error, average of true outs, and another interesting graphics so I've decided do it, I think to use Gnuplot to do this analysis, but I need some advices or things that i do wi... |
I'm having problems with powerTransform - for example it has just failed to transform a perfectly ordinary (to me) looking variable, with the following error
Error in optim(start, llik, hessian = TRUE, method = method, ...) :
L-BFGS-B needs finite values of 'fn'
Here is the data: http://www.tropic.org.uk/~crispin/bo... |
I have some time series data where the measured variable is discrete positive integers (counts). I want to test if there is an upward trend over time (or not). The independent variable (x) is in the range 0-500 and the dependent variable (y) is in the the range 0-8.
I thought that I answer this by fitting a regression ... |
I have a question about the normalization in case we use weigthed last squared. By normalization i mean the column of the predictor matrix $X$ have unitary variance. In case of WOLS i weigth each observation $y_i$ and predictor $x_i$ with a weigth $w_i$.
$$\min\sum_{i=1}^n (w_i y_i - \beta w_i x_i))^2 $$
$$=\min (Y-\... |
It's been a while since I've thought about or used a robust logistic regression model. However, I ran a few logits yesterday and realized that my probability curve was being affected by some 'extreme' values, and particularly low ones. However, when I went to run a robust logit model, I got the same results as I did in... |
I have Groups A, B, and C. My hypotheses are:
Proportions of C are different from proportions of B (=independance)
Proportions of A are NOT different from proportions of B (=NO independance)
Results:
A: success = 0.085 n=50
B: Success = 0.167 n=50
C: Success = 0.380 n=50
If I do post-hoc contrasts using the pairwi... |
I'm testing for difference in a continuous outcome under three different conditions.
Under condition A I take a measurement of the outcome. I do this twice for the same sample. Example values could be 2.2, 2.1. These are "technical" replicates that come from the same biological source
I do the same for four "biologica... |
I have some data that I know are related but I can't seem to find the exact relationship. Was hoping someone could help find it. Left column data is related to the right column.
1160786507 E02K
1432646245 Udre
1211119187 H06S
1214345830 HARF
1211117653 H00U
1429221446 U00F
1430466865 ... |
I am studying Larry Wasserman's lecture notes on Statistics which uses Casella and Berger as its primary text. I am working through his lecture notes set 2 and got stuck in the derivation of lemma used in Hoeffding's inequality (pp.2-3). I am reproducing the proof in the notes below and after the proof I will point out... |
I'm currently trying to analyze Tweets and classify them as either positive, negative, or neutral using the NLTK library in Python.
I can see that there's potential in the approach that I'm taking, however, I'm having trouble with my feature selection process.
Indeed, input from Twitter isn't exactly conventional, so ... |
I'm doing timings of an application which speeds up as we add threads. However, the times vary on repeated runs. What I'd like to have is a speedup chart which shows how many times faster than the baseline the application is, for each thread count I test on.
The data I was planning on gathering was 5-10 runs for each... |
I have a model where I assumed a variable X would have an exponential decay over time t. I modeled it in R as
$$N = N_1e^{kt},$$
where $k < 0$ and $t$ is 1:95.
However, looking are some real data that I have captured, it seems that the decay is slightly slower to begin with but is much faster towards the end. The grea... |
I'm trying to understand the derivation of Expected Prediction Error, as described in The Elements of Statistical Learning. Specifically, it says:
$EPE(f) = E(Y - f(X))^2$
By conditioning$^1$ on X, we can write EPE as:
$EPE(f) = E_XE_{Y|X}([Y - f(X)]^2 | X)$
And, a footnote for this says:
$^1$Conditioning here amou... |
Consider the model in spatial econometrics denoted SAR by James P LeSage:
$y = \rho W y + X \beta+ \epsilon$
I use the R package spdep and the econometric toolbox by LeSage from www.spatial-econometrics.com. However, when comparing the way these two compute the residuals there are differences. The R package by Roger Bi... |
Crux of the question
Let $q \sim F$ with support $[0,1]$. Let $q_j$ be the $j$th order statistic of $N$ draws from $F$. Let $z_j \sim \text{Bernoulli}(q_j)$. See that these draws are independent, given the $q$ probabilities. We need to know
$$\begin{equation*}\Pr(z_{1} = 0, \dots, z_{j-1} = 0 | q_{j} = x);\end{equation... |
I have to find a 95% C.I. on the median and other percentiles. I don't know how to approach this. I mainly use R as a programming tool.
|
I have 365 daily measurements that all have standard errors associated with them.
Date | Prediction | Standard Error
-----------------------------------------
Jan-01-2003 | 24.8574 | 10.6407
Jan-02-2003 | 10.8658 | 3.8237
Jan-03-2003 | 12.1917 | 5.7988
Jan-04-2003 | 11.1783 ... |
New to MCMC.
I have a model, saying
$$Y_i=\beta_0+\beta_1x_{i1}+\beta_2x_{i2}+\frac{e_i}{\sqrt{\mu}}$$
where $x_{ij}$ are fixed covariates, $e_i\sim N(0,1)$, $\beta_0$, $\beta_1$, $\beta_2$ and $\mu$ are unknown parameters, with the prior distribution for parameters $\beta_i\sim N(0,1)$ and $\mu\sim \Gamma(0.1,0.1)$
No... |
It occurred to me that how one writes an interaction term in BUGS depends on the types of predictors that are "interacting". Suppose data that are long (rather than wide). Then, a model with an interaction between two factors, A and B, as in two-way ANOVA, may look something like
y[i] ~ dnorm(mu[i], tau)
mu[i] <- A[a_l... |
How can I compare whether classifiers outcome is significantly different?
I have a relatively small data set which I'm trying to classify. My training set consists of 24 items come from two different groups, 12 items from each group. each item has two properties. I have 12 new items which I would like to classify base... |
Assuming the following model (Fir instant, received signal of a communication / RADAR system):
$$ x[n] = \alpha s[n] + w[n] $$
Where:
$ s[n] $ is a known signal of length $ L $ and known energy $ p = \sum_{n=0}^{L-1} {s}^{2}[n] $.
$ \alpha $ is unknown attenuation factor. Though it is known $ 0 < \alpha \leq 1 $.
$ w[... |
I am trying to reproduce the anova table for a 2x2 cross-over design. I used the data listed in tables 2.1 and 2.2 of the "Design and Analysis of cross-over trials" book, by Jones and Kenward. I am giving all the code so that you can reproduce the calculations.
g1AB <- read.table(textConnection("
Label Per1 Per2
7... |
I have preformed multiple tests and now have a list of all the calculated P-Values (~30K^2 values). I have a reason to believe my tests are somehow dependent.
I would like to analyze the results and correct the p-values.
Unfortunately, I only have very basic knowledge in statistics. From the little I managed to gather,... |
Having a map such as:
How to find major directions of variation i.e., for the example given here: north-east--south-west? in an elegant, quick and clean way?
Any ideas are more than welcome.
|
I am aware of the fact that Gosset came up with t-distribution, but what is the etymology of "t"? How did "t" end up in t-test and t-distribution?
|
I've been given a set of 20 Likert-items (ranging from 1-5, sample size n = 299) within the field of organizational research. The items are intended to measure a latent concept which is multidimensional, multifaceted and heterogenous in it's very nature. The goal is to create a scale(s) which can be nicely used to anal... |
In fitting a polynomial $p_N = \sum\limits_i^N a_i x^i$ to my dataset $(x,y)$ using a least squares criteria, I'm interested in determining the optimal polynomial order $N$. The caveat is that, owing to problem specific restrictions, the polynomial must satisfy the following boundary conditions: $p_N(0) = 0$, and $\fra... |
Can you recommend a book with good information that can be applied to developing a recommender system?
|
I'm taking a statistical learning class, and I need to brush up on my calculus. I already took calculus and probability several years ago, but I have a bad memory.
Are there any good books or general resources that give a review of calculus with a probability and statistics slant? I noticed that most calculus books giv... |
Considering a simple linear regression model Y= beta0+beta1 x X, with beta0 and beta1 computed, I have to estimate the expected X given a new Y and 95% confidence intervals.
I used the formula X=(Y-beta0)/slope. How can I compute in R the 95% interval for the calculated value of ind, given a new value of the height?
... |
My team manages a survey that has been reporting for many years as "relative sample error" a range of figures which are in fact the Xs in "+/- X percent" of an estimate where X is chosen to make up a 95 percent confidence interval. So in fact they are about 1.96 times the relative standard error. The users - who are ... |
I have six 5-point Likert items (1-Strongly Disagree, 2-Disagree, 3-Neither agree or disagree, 4-Agree, 5-Strongly Agree) which are related to my dependent variable. I sum the six variables which gives the frequency as follows:
Frequency
6.00 1
9.00 1
12.00 6
13.00 3
14.00 3
15.00 18
16.00 11
17.00 ... |
This question arises from the one asked here about a bound on moment generating functions (MGFs).
Suppose $X$ is a bounded zero-mean random variable taking on values in
$[-\sigma, \sigma]$ and let $G(t) = E[e^{tX}]$ be its MGF. From a bound used in a proof of Hoeffding's Inequality, we have that
$$G(t) = E[e^{tX}] \leq... |
I am looking for a package to analyze rank-order data in the form of regression. My outcome (dependent) variable is a rank ordering in the sense that the respondents to a questionnaire were asked a single question: to assign the values 1 to 4 to four different objects (e.g. to rank four cars as best , second best etc)... |
I have two datasets, the first on schools, and the second lists students in each school who have failed in standardized test (emphasis intentional). The first dataset has the structure below (I'm sorry I could not figure out how to insert a proper data snippet):
School_ID Total_White Total_Black Total_Asian Sch... |
Possible Duplicate:
A reliable measure of series similarity - correlation just doesn't cut it for me
I'm trying to determine a method to compare one particular time series against about 10,000+ reference time series programmatically, and shortlist those reference time series which can be of interest.
The method I wa... |
Random forests are considered to be black boxes, but recently I was thinking what knowledge can be obtained from a random forest?
The most obvious thing is the importance of the variables, in the simplest variant it can be done just by calculating the number of occurrences of a variable.
The second thing I was thinking... |
I am asked by colleagues some help in this subject, that I don’t really know. They made hypotheses on the role of some latent variables in one study, and a referee asked them to formalize this in SEM. As what they need doesn’t seem too difficult, I think I’ll give it a shot ... for now, I am just looking for a good int... |
I'm approaching at pattern recognition with HMM (with c++ or python).
My data are x and y coordinate (normalized between -1,1) of the hand in a recorded video and I want to recognize.
This is what I have understand to classify a hand that make a gesture (for example a circle):
I need some train data (for example N dif... |
I have a collection of real-world samples that I am trying to model and then forecast.
There are 10 datasets – each has an increasing number of data points (from 1 to 10). The points are equi-distant and each has some percentage of the total allocation for that set. For example, the first set has 1 data point with 10... |
I have event time data for subjects with different categories (A, B, C etc.) yearly observed. To my understanding my data is both right and interval censored (?).
Subjects' category can change from year to year, e.g. A for years 0 to 2, than B from year 3 onwards for subject 1 etc. Each subject can be exposed to the "... |
I want to use Excel to generate a random correlated $Y$ from a known $X$. From another thread, I found the equation $Y = r\cdot X + E$, where $X$ is standardized and $E$ is a random variable from normal distribution having mean $0$ and $\sigma = \sqrt{(1-r^2)}$. I assume $r$ is the correlation coefficient found using... |
I have a number of measurements of a data point which I want to compare to my model. I have the sample mean, sample standard deviation and therefore the SEM. It usually seems fairly obvious to me whether to use the std. dev. or SEM. I think in this case I want to use the std. dev. as I'm comparing my model to my data, ... |
I have a linear regression and two estimates, say A and B and their standard errors. I need to find the standard error of a ratio A/B [or A/(1-B)].
I guess the main problem is that I don't know the correlation between A and B. I also guess that makes this unsolvable, since the correlation plays a major role. Is this co... |
I have a random effects panel data model with 4 variables, 10 years of data and 946 observations describing different financial values for different companies. The panel is balanced. The model looks something like (written without subscripts t for time and j for company): $ln(A)=b0+b1(ln B) + b2 (ln C)...+u$
However, w... |
I have a small (n ≈ 15) IID sample from a continuous distribution that I have no reason to believe (a priori or a posteriori) belongs to a familiar parametric family. I do know a priori that the distribution is bounded, and I know its bounds, but that's about all I know. I'd like to construct 95% credible intervals for... |
I am trying to solve for the parameters in the maximum entropy problem in R using the nonlinear system:
$\ \int_l^u e^{a+bx+cx^2}dx=1$
$\ \int_l^u x e^{a+bx+cx^2}dx=\mu$
$\ \int_l^u x^2 e^{a+bx+cx^2}dx=\mu^2+\sigma^2$
where $l$ and $u$ represent the lower and upper bound on the support of the distribution, and $a,b,c$ ... |
So I hear the term 'testing a model' used a lot. There seems to be a variety of ways to find whether a model has explanatory power (R^2) or if there is an overall significant relationship between the variables (g-test). However, let's say I have data which I acquire each day. Let's say I ran a logistic regression on th... |
In Example 4.4.2 on page 163 of Statistical Inference, the following is implied:
$\sum_{t=0}^{\infty}\frac{((1 - p)\lambda)^t}{t!} = e^{(1-p)\lambda}$
with a note that says "[the] sum is a kernel for a Poisson distribution". I understand the Poisson distribution, but I don't fully grasp the kernel concept yet. I tried ... |
A random variable usually has a definition like "a function that maps from the original sample space to a new sample space, typically a set of real numbers". Is it ever useful to map into a new space that isn't a set of real numbers?
|
Which distributions are their own Fourier transform besides the normal distribution and the generalized arcsine distribution?
|
Let's say I have a list of 100 MLB pitchers and 5 statistics for each of them. The difference between, for example, an ERA of 3.5 and 3.1 might not look like a lot to a naive similarity algorithm, but is a lot in baseball. Given that a lot of the player statistics that I'm looking at have this little variance, a lot of... |
I have two basic models $M_1$ and $M_2$. They each have a likelihood function;
$L_{M_1} = f(\mathbf{X}|\mathbf{\theta_1})$ and $L_{M_2} = f(\mathbf{X}|\mathbf{\theta_2})$ (here $\mathbf{X}$ is the data set, and $\mathbf{\theta_i}$ are the parameters for the model). The models are nested since model $M_1$ parameter's a... |
I have two sample data sets which are each a 1x95 vector containing the $\lambda$ of a Poisson. Each slot contains the $\lambda$ for the minute that the slot represents. So t1[1] is the starting lambda, t1[2] is the $\lambda$ after one minute, etc. The value of the lambda slowly decays over the time series. The series ... |
How conservative is Benjamini-Hochberg multiple testing correction relative to the total number of comparisons? For example, if I have a list of 18,000 features for two groups and I perform a Wilcoxon test to get a p-value. I adjust that p-value using Benjamini-Hochberg and next to nothing comes out as significant.
I ... |
Let's say I want to perform an AB-Test with the following properties:
We assign unique visitors to each group, not the requests (so each trial corresponds to a unique visitor as long as e.g. the cookie is not deleted)
We want to measure "items viewed" per unique visitor (side note)
The question now is: How to define ... |
I'm trying to determine a method to compare one particular time series against about 10,000+ reference time series programmatically, and shortlist those reference time series which can be of interest.
The method I was using was Pearson Correlation. For each of the reference time series, I would calculate their correla... |
If Stouffer's method of combining $k$ probabilities is based on the variance of the sum being equal to the sum of the variances, and the variance of $z$ is $1$, why does the Stouffer's formula divide by the square root of $k$ rather than by $k$?
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I am doing a simple study that involved taking a measure at time point 1 and time point 2 (12 weeks later). While the sample was a class, not all members were present at both time points, so I have 20 date points at time 1 and 21 date points at time 2. The measure has a score, and I am taking the means and doing a si... |
Are additive logistic regression and boosted decision stumps (where a decision stump is a one-node decision tree) equivalent in some sense? I thought not, but if I google for "LogitBoost" algorithms, I find:
http://weka.sourceforge.net/doc/weka/classifiers/meta/LogitBoost.html, which says it's a "class for performing ... |
I'm doing some research about methods for distance-based comparison of composition of biological sequences (genes, proteins).
Suppose I have two strings (named X and Y) of different lengths, but from a finite alphabet (A, C, T, G):
X = 'ACGT'
Y = 'ACGTA'
The difference between two strings can be quantified by calcula... |
I am a PhD student with some difficulties about what test to choose to verify an experiment. Hope you can give me some help!
My experiment:
I am counting the number of a subset of cells in Drosophila overtime.
I have a mutant and a wild type control. I dissect the flies at different time points: just eclosed, 1 day aft... |
I have a questionnaire where some of the questions concern ranges, the answer alternatives are:
0
1 - 15
16 - 30
31 - 45
46 - 60
60+
(the numbers are minutes per week, not that it matters)
If I would like to present the result as an average number, how would I do this?
My thinking right now is just to take the avera... |
What are the best (recommended) pre-processing steps before performing k-means?
|
I am so puzzled by this problem.
Given two variables $X_1$ and $X_2$, such that $X_i \sim \mathrm{Gam}(a_i, b)$, find the joint distribution of $X_1$ and $X_2$.
I understand how to proceed if variables are independent, but the general case is a bit unclear.
Thanks for your help!
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Is there a difference between ANCOVA (as performed under the 'General Linear Model (GLM)') and Hierarchical Regression (as performed under 'Regression') in SPSS?
I am testing the main effects and interaction of X1 (continuous) and X2 (categorical) on Y (continuous).
I understand GLM incorporates regression and one of t... |
I am running a least squares regression, and I am trying to estimate the uncertainty on the fit solution. The problem is, I have an uncertainty in my design matrix coefficients as well as in my predictors. So given $||Ax - b||_2$ being minimized, and uncertainties $\sigma_b$ and $\sigma_A$ on the coefficients of $b$ an... |
Why is Stouffer's method so often performed on $z$'s that correspond to one-tailed $p$-values, when the mathematics allows for $z$'s that correspond to two-tailed $p$-values?
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As I understand it, I need to know at least three aspects (out of four) of my proposed study in order to conduct power analysis, namely:
type of test - I intend to use Pearson's r and ANCOVA/Regression - GLM
significance level (alpha) - I intend to use 0.05
expected effect size - I intend to use a medium effect size (... |
A short mice-related question as follows: when running simple mice imputation the function goes through well. But complete() function does not substitute my NA's at all. I guess it must be something wrong with my dataset but I can't see what. It is just a matrix as any other although with roughly equal number of rows a... |
I have written a little function that samples from a normal distribution with linearly changing variance
rnormltv <- function(n,mu,rsd) {
vc <- vector(mode="numeric", length=n)
i <- 1
for (x in seq(from=rsd[1], to=rsd[2], length=n)) {
vc[i]=rnorm(1,mu,x)
i <- i+1
}
return(vc)
}
Supp... |
I am comparing tree species use vs. availability within bird territories. I am using the R compana() function which uses Aebischer et al. (1993) method (package adehabitatHS) to determine if there are significant differences in proportional availability and proportional use of different tree species.
I am trying to de... |
Imagine you were interested in student dropout rates across schools over time. You had data on the number of dropouts, but not the number of students enrolled at each school-month.
A single dropout for a school with 10 students is a higher relative rate than 2 dropouts in a school of a 100.
An increased number of obser... |
I have a large dataset consisting of many features for each record which includes either a GOOD or BAD outcome. Three metrics have been created for classification purposes using three respective Bayesian Belief Networks:
Classification Network including outcome variable trained on both GOOD and BAD records
GOOD Networ... |
I am performing simple (first-order terms) linear regression on data having several categorical variables (i.e. factors), and it is often desired that for each factor, one of the levels should add nothing to the regressand, and the other levels should add positive values to the regressand. When I perform a regression ... |
I am new to Bayesian statistics, and thus have problems to come up with a solution for the following problem:
Using Approximate Bayesian Computation (ABC), I generate a posterior distribution from one set of observed summary statistics, and a set of about a million simulated summary statistics. The prior distribution i... |
I am currently working to build a model using a multiple linear regression. After fiddling around with my model, I am unsure how to best determine which variables to keep and which to remove.
My model started with 10 predictors for the DV. When using all 10 predictors, four were considered significant. If I remove only... |
I have some time series data of measurements taken at random intervals with dimensions >> measurements, with intervals anywhere between 15 seconds and a few minutes. Ideally I would like to have a continuous time estimate to give me the state of the system at any time between the beginning and end of measurements with ... |
In a multiple linear regression I have one predictor showing a cubic relationship with the outcome. If the same predictor $A$ is also part of an interaction with a continuous variable $B$, do I have to apply the polynomial transformation to both terms?
$$
\hat{Y} = {c} + \beta_1{A} + \beta_2{A^2} + \beta_3{A^3} + \beta... |
Can anyone give me advice on computing the asymptotic confidence intervals for a difference in quantiles of a distribution? For example, I have fit a log-normal distribution to doubly interval censored data with a maximum likelihood estimator and want to make statements about a percentage of the probability mass falli... |
I'm relatively new to survival analysis and try to get my data in the right shape.
I have two tables both concerning the observed individuals. If I just would use one of the tables, I would have continuous information on each individual without any overlapping periods.
As I however also need the information stored in t... |
I need a little help to move in the right direction. It's a long time since I studied any stats and the jargon seems to have changed.
Imagine that I have a set of car-related data such as
Journey time from town A to town B
Distance from town A to town B
Engine size
Driver's shoe size
Make and model of car
Day of week... |
I have six scatterplots (such as the one below) that show an insignificant interaction of the factor (X2) (e.g. gender, age, education etc.) with the predictor (X1) on Y. (X1 is significant.)
The simplest interpretation is that as X1 increases, Y increases for both levels of the factor (in this case, males and females... |
Here are my experimental factors:
within-factor (two levels): time1, time2.
between factor (four levels): 4 groups.
I want to test specific post-hoc contrasts comparing:
group1: time1 vs. time2
group2: time1 vs. time2
group3: time1 vs. time2
group4: time1 vs. time2
to determine if and which group the time factor a... |
Suppose you have a discrete random variable, $Y$, with a large number (say, $300$) of discrete (which happen to be nominal) possible outcomes. The mass function, $p(y)=P(Y=y)$, is unknown but a sample is taken from $Y$ from 20 populations $i=1,2,...,20$. Let $Y_{ik}$ be the $k$'th sample from the $i$'th population and ... |
I am on a self-experiment quest to solve some health related problems I have, and I want to create a self-survey that I take every day. What's the best way to codify the survey so I can later analyze the data? I am not a statistics guru, as you can tell, so I'm probably asking a pretty basic question here. For the s... |
I have 2 general/more theoretical question.
1) I'm curious how SVMs handle variable interactions when building predictive models. E.g., if I have two features f1 and f2 and the target depends on f1, f2, and say f1 * f2 (or some function h(f1, f2)), does SVM fit (not just on OOS but even on training data) improve when i... |
A coin needs to be tested for fairness. 30 heads come up after 50 flips. Assuming the coin is fair, what is the probability that you would get at least 30 heads in 50 flips?
The right way to do this problem, according to my teacher, is to do
normalcdf(min = .6, max = ∞, p = .5, σ = sqrt(.5 * .5 / 50) = 0.0786
Howev... |
I have two proportions (e.g., clickthrough rate (CTR) on a link in a control layout, and CTR on a link in an experimental layout), and I want to calculate a 95% confidence interval around the ratio of these proportions.
How do I do this? I know I can use the delta method to calculate the variance of this ratio, but I'm... |
Note: I do not have access to SAS to work this out for myself.
I'm trying to work out the difference between the FREQ statement in PROC GENMOD (for example) and the REPLICATE statement in PROC NLMIXED.
The SAS explanation is not illuminating the practical mathematical difference for me. The explanatory test for REPLICA... |
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