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I am looking at whether abundance is related to size. Size is (of course) continuous, however, abundance is recorded on a scale such that
A = 0-10
B = 11-25
C = 26-50
D = 51-100
E = 101-250
F = 251-500
G = 501-1000
H = 1001-2500
I = 2501-5000
J = 5001-10,000
etc...
A through Q... 17 levels. I was thinking one possib... |
I want to perform in R the analysis "simultaneous confidence interval for multiple proportions", as illustrated in the article of Agresti et al. (2008) "Simultaneous confidence intervals for comparing binomial parameter", Biometrics 64, 1270-1275.
Unfortunately I did not succed to find any R example, and I have no idea... |
I am trying to visualise some consumer data, which has 4 categories. Users are free to switch between different categories. I would like to visualise the last three or four switches for each individual.
So we would start with a plot with a column with 4 stacked proportions. After that we would have 16 as each category ... |
Suppose you have a classifier $C^n$ which continuously outputs a stream of classification labels $K^n_i$ and corresponding timestamps $T^n_i$. Also, we know the prior probability $P(K^n) \forall n$. Now, suppose we have several classifiers obtaining classification labels from different sources of data but all attemptin... |
I am trying to get the raw value of AIC that I can see as a result of the summary function.
x = forecast(ets(ts(data, start=2000, frequency=12)),h=6)
summary(x)
This shows me an AIC value:
AIC AICc BIC
7.995437 27.995437 7.779078
When I use AIC I get this error
> aic <- AIC(x)
Error in UseMethod("logLi... |
I have univariate time series data (windspeed at a particular place) measured at 1 hour interval for 5 years.
I used auto.arima() to get the following parameters:
ar1 ar2 ma1 ma2 intercept
1.5314 -0.55 -0.1261 0.032 10.1223
s.e. 0.0105 0.0103 0.011 0.006 ... |
Scenario Construction:
I have a MFCC generator block which gets the speech samples from the user and generates a rectangular matrix say $A$ of the order $m \times n$, whose elements are the Cesptral Coefficients(MFCC). Now, suppose I maintain a database which are previously stored containing the user speech signal. Thr... |
I want to proof the "Relative Age Effect" of a football team. I have a list of birth dates of the team members (about 20 numbers between 1 and 365, the day of the year).
I now want to use the KS-Test to test against a uniform distribution.
this is how I did it, but it looks very wrong to me:
ks.test(dates,"punif")
D =... |
I am working on a machine learning project where I am trying to fit a curve on data. Unfortunately the date has somewhat high feature vector. So, I can't really plot them on a 2D or 3D space to guess how the shape of the data looks like.
So, other than hit and trial, does there exist a mathematical way to find degree ... |
I have a dependent variable ($y$ axis in the pictured graph) trending over time ($x$ axis). I also have a categorical variable, which was constant until one point in time, then changed to another value, with which value it has remained constant since; that point in time is indicated in the picture by a break in the pic... |
I have two (vehicle velocity) signals that should consist of similar "latent" drivers, but have different autocorrelation structures. The driver-signals are quite nasty statistically, so I'm not attempting to model them.
I can get quite nice results by prewhitening the signals using AR(1)-residuals, but these are very ... |
I'm trying to look at multiple comparisons (across levels of my between subjects factor) for a model with one between-subject factor and one within-subject factor. I was trying to use TukeyHSD on an aovlist object, and then found out that I couldn't do that.
After some browsing, I found how to do what I wanted using lm... |
When trying to evaluate what constitutes a family of hypotheses within an experiment/project/analysis, I've found "similar in purpose" and "similar in content" given as guidelines for delimiting families, but these leave quite a lot open to interpretation (to say the least).
It seems clear that if in the course of an a... |
Background
I've recently read the paper
Leo A. Goodman, On the Exact Variance of Products
Journal of the American Statistical Association
Vol. 55, No. 292 (Dec., 1960), pp. 708-713
from where I extract the following edited quotes (removed superfluous calculations and sentences)
Let $x$ and $y$ be two independent rand... |
Let $X_1$ be a random value from distribution 1 and let $X_2$ be a random value from distribution 2. I thought that the null hypothesis for the Mann-Whitney test was $P(X_1 < X_2) = P(X_2 < X_1)$.
If I run simulations of the Mann-Whitney test on data from normal distributions with equal means and equal variances, with ... |
I have done a linear regression and plot the residuals. I noticed that the errors are dependent(autocorrelated), how could I test homoscedasticity of this series? I read that Breusch-Pagan test only work with independent errors.
What test could I use to test if the variance is constant in this case?
|
How Breusch-Pagan can't reject the null for a series like that?
> x = c(rnorm(10), rnorm(100,sd=10), rnorm(100,sd=25))
> mod = lm(x[-1]^2~x[-210]^2)
> plot(mod$res,type='l')
> bptest(mod)
studentized Breusch-Pagan test
data: mod
BP = 1.1085, df = 1, p-value = 0.2924
The variance change drastically, could s... |
We are often confronted with brand attribute associations (Yes/No) in Market Research, and more often than not we need to do Factor Analysis (we use PCA under Factor in SPSS) in order to reduce the data to something useful and interpretable.
What is the best method of data reduction when you have binary data? Surrogat... |
Best statistical method for analysing a single clubs football (soccer) results?
I have every result for over 100 years in date order. Is there a recognised or recommended method for analysing results, making some sort of coefficient to help in predicting results or at least showing +/- progress based on each result.
ap... |
Let's say we are interested in approximating the following expectation:
$$\mathbb{E}[h(x)] = \int h(x)\pi(x) dx$$
Where $h(x)$ is an arbitrary function and $\pi(x)$ is a distribution known only up to a normalizing constant. We could approximate this expectation using a Metropolis-Hastings sampler to draw samples $\{x_... |
I have a multiple linear regression model, and need to test the significance of the slopes. My professor says that there are two ways to go about it - so which should I use? The questions in the exam would have the standard error of the regressors along with the estimated value of the regressors as well.
|
I am wondering if anyone knows of a way to run a multiple mediation model in R. I know the mediation package allows for multiple simple mediation models, but I want to run one model that evaluates multiple mediation models simultaneously.
I am assuming I can do this in an SEM framework (path analysis), but was wonderi... |
I am trying to calculate kappa scores for present/absent decisions made by two raters and I have heard that they can be adjusted for prevalence of the object of measurement.
Can anyone advise on how to calculate a kappa statistic that is adjusted to account for prevalence of the object of measurement?
|
I have been collecting the number of new followers every day for about 6 months for 30 different twitter accounts and I know the exact time that they started following. I have been also collecting all tweets for these accounts during this time period.
I'm interested in whether some independent variables (tweet rate, nu... |
I am tasked with bringing up an SPC system within our moderately sized, but very technical, manufacturing company.
It might be against the rules of this forum, or maybe bad form, to name specific companies, although if anyone is comfortable doing that, I'd certainly appreciate it (providing the opinion is fairly unbias... |
There was a post once upon time dealing with the differences of multivariable and multivariate regression. I have seen the relevant post here. However I am having this debate with a colleague and while I agree with the information of this post, my colleague insist that multivariable regression is actually just multiva... |
I don't understand why reduction in dimension is important. What is the benefit of taking some data and reducing their dimension?
|
I am attempting to impute my data for missing values using the mice function (from the mice package) in R. However everytime I run the function it freezes or lags.
I have tried running it over night, and it still does not finish. I am working with 17000 observations across 32 variables. I can't even stop the function ... |
As I understand it, matching is one way to identify causality in observational studies. By matching observations that are "similar" and comparing ones that did or did not receive treatment, you can consider this as a quasi-experiment of sorts.
What is overmatching? What kind of bias does it introduce? I have mostly see... |
I've heard a bit about using neural networks to forecast time series, specifically recurrent neural networks.
I was wondering, is there a recurrent neural network package for R? I can't seem to find one on CRAN. The closest I've come is the nnetTs function in the tsDyn package, but that just calls the nnet function f... |
Logistic, linear and probit regression can be written in terms of Generalized Linear Model (GLM). Can the multinomial logit regression be written in terms of GLM as well?
|
I'm modeling some periodic data with a second-order autoregressive model, as follows:
$$
x_3 = a_{1}x_1 + a_{2}x_2
$$
$$
x_4 = a_{1}x_2 + a_{2}x_3
$$
$$
...
$$
$$
x_n = a_{1}x_{n-2} + a_{2}x_{n-1}
$$
I'm modeling the raw data here (imagine $x_i$ as a scalar pixel value, say, for $n$ time points) so I'm not worr... |
I am just trying to understand what the relationship is between a normal multiple/simple regression vs. multiple/simple regression when the variables are differenced.
For example, I am analyzing the relationship between deposit balance ($Y_T$) vs. market rates ($R_T$)
If I run a simple linear regression, the correlatio... |
I submitted the final in a theoretical stats class and had trouble with several problems, but part of one is bugging me because it seems like it should be simple. Lets say we have two random independent variables $X$ and $Y$, each with their respective pdf $f(x)$ and $f(y)$. The support for each is:
$-\infty < X < \i... |
Some Quick References for statistics.
conditions:
1- offline, i.e., independent from internet
2- soft-copy, i.e., (workable on a computer) not a hard-copied book or etc
3- intermediate to advanced a comprehensive
4- not an encyclopedia with many links to that page or other term
5- ...
6- free or almost free
7- reliable... |
I originally asked the question in this post, where I explained that I only have 25 measures at my disposal. Hence, computing the sample SD $\sigma_x$ and assume it's the one from the distribution looks to be very optimistic and I wanted to compute a confidence interval.
It was suggested to me to use the bootstrapping ... |
Supposing $g(x)=\sqrt[3]{x}$, I want to calculate the expected value of g, $E(\sqrt[3]{x})$, using Monte Carlo method, by generating $x_i$ from a Weibull distribution with parameters $(1,5)$.
After that, I want to use the control variates method and the antithetic method in order to to reduce the variance of my estimat... |
Consider a sequence of independent random variables $(y_k)_k$ with a
probability density $p_{\theta}(y)$ depending upon only one scalar
parameter. Before the unknown change time $t_0$, the parameter
$\theta$ is equal to $\theta_0$, and after the change it is equal to
$\theta_1 \neq \theta_0$. The problems are ... |
Which is a better cost function for a random forest tree: Gini index or entropy?
I am trying to implement random forest in Clojure.
|
This question is related to a few others (Here,Here) on the topic as I have been searching for information. Hopefully this one is sufficient.
1) I am seeing differences in the relationship between survival at time t, S(t) and the hazard at time t, h(t).
In Singer and Willet page 337 (10.5) they define the estimated sur... |
I have two variables, response and group, and I fitted the model in which group is a random effect.
proc mixed data=myData nobound;
class group;
model response =;
random group;
run;
However, SAS returns a negative variance for the random effect...
I have noticed that, unexpectedly, the variability of response... |
I'm trying to test a program that claims to calculate some statistical properties of a numeric sequences (like mean, median, standard deviation etc). Simple and short sequences pass the test well, but I'd like to challenge the program with either long sequences, or sequences with large and small values (to test overflo... |
I did an experiment with 12 participants. They were asked to rate 3 stimuli, with the following 3 possible answers: "increased", "decreased", "no difference".
I have as a result this table:
Increase Decreased No_difference
StimulusA 10 1 1
StimulusB 12 0 0
StimulusC 8 ... |
Every time I look at SAS's result page I get lost among the numbers.
Is there any online material that can help with understanding SAS's result page?
|
Here is the problem from the book:
Let $X = \min(U,V)$ and $Y = \max(U,V)$ for independent $\text{uniform}(0,1)$ variables $U$ and $V$. Find the distributions of a) $X$; b) $1-Y$; c) $Y-X$.
I know that each has density $2(1-x)$ for $0<x<1$. What I'm hoping for is an intuitive explanation of how to understand this p... |
Given a sorted set of data points, where each point represents the length of a common substring between two files, I want to systematically decide a cut off point where I can start considering them to be "short" and no longer care about them.
Basically my goal is to exclude the data points that represent commonalities ... |
I have gotten a student job in the management department of a chain of 50 grocery stores. The job includes gathering daily statistics on the economy of the stores.
Every day a per-store revenue statistic is made, comparing the revenue to matching day last year (sunday/sunday, monday/monday) and an accumulated statistic... |
I take vitamins in the morning, but one of them I only take a half tablet.
So, I have an initial container with 100 full tablets, and every morning I take out a random tablet. If it's a full tablet, I break it in half, put half back, and take half. If it's a half tablet, I just take it. Given that, how many days m... |
Is there some way to create a bivariate distribution from a fitted copula and 2 marginals? I have finally managed to fit a copula to my stock returns using the package fCopulae and would like to calculate the VaR of a portfolio consisting of these two stocks. As far as i can tell, this can be done by simulating from th... |
If we wish to conduct a paired t-test, the requirement is (if I understand correctly) that the mean difference between the matched units of measurement will be distributed normally.
In paired t-test, that is articulated (AFAIK) in the demand that the difference between the matched units of measurement will be distribut... |
Does the survivor function estimated after running a Proportional Hazards model give valid predicted probabilities of an event happening after a number of time periods?
The only source I've found on this question says that Proportional Hazards estimates can only be used to discern the factor that two hazards rates diff... |
This is a followup question to what Frank Harrell wrote here:
In my experience the required sample size for the t distribution to be
accurate is often larger than the sample size at hand. The Wilcoxon
signed-rank test is extremely efficient as you said, and it is robust,
so I almost always prefer it over the t t... |
I have two square symmetric matrices, A and B, each of which contains the pairwise cosine distances between two different sets of vectors. The sets of vectors are different for A and B, but they are correlated. The original vectors from which these distance matrices were constructed are no longer available. These matri... |
I have a dataset to analysis and the following information is known:
$y_i \sim N(\mu_i, \theta(\mu_i)^2)$
The link function is => $ln(\mu_i) = (\beta)^T X$
$y_i$s are count data. The model parameter is beta and theta.
I need to find an estimation method and fit a model.
I have looked at the over-dispersion model and ne... |
I have counts of people with a condition, by age (5-year groups), sex, and area (100-200 areas).
For each area, I have:
estimated population by age (5-year groups) and sex,
estimated population percent living in city, small town or rural (sum
to 100%),
estimated population in high, middle and low socioeconomic status
... |
I recently took an introductory course on multilevel modelling. Most of the datasets and examples we used were from the social sciences. I've just got a 2 week internship in a biostatistics department, where they want me to start a project concerning the variation at hospital level of patient outcomes for an emergency ... |
I'll try to compute different similarity measures on some data. The result is always a similarity matrix on the data.
I want to evaluate the quality of the matrix by checking if the values for positive and negative similarities have a wide spread so that one can set an threshold which is very general to all data. Mean... |
Say I have N observations, possibly multiple factors and I repeat each observation twice (or M times) how would a regression on this new set of size NM compare to a regression on just the original observations?
|
I have two positively correlated variables, Q95 (independent, 95-percentile flow in cumecs from the previous summer) and LIFE (dependent, a score describing the health of some invertebrates). I would like to be able to predict, to some degree of confidence, what value of Q95 is required to attain a given LIFE. From wha... |
I'm currently stuck on this data, trying to figure out what test is needed. I started thinking it needed an ANOVA test but on reading, figured it was a Chi Squared test. On more reading, that doesn't seem right either.
The data I have is in a table as such:
Damage Group 0 minutes 2 minutes
11 40.17 ... |
I am interested in knowing whether or not there is a consensus about the optimal way to analyze hospital length of stay (LOS) data from a RCT. This is typically a very right-skewed distribution, whereby most patients are discharged within a few days to a week, but the rest of the patients have quite unpredictable (and ... |
Consider $\sum_{i=1}^N |X_i|$
where $X_1, \ldots, X_N$ are i.i.d. and the CLT holds.
How many of the biggest terms add up to half the total sum ?
For example, 10 + 9 + 8 $\approx$ (10 + 9 + 8 $\dots$ + 1) / 2:
30 % of the terms reach about half the total.
Define
$ \qquad\text{sumbiggest( j}; X_1 \dots X_N ) \equiv
... |
Lets assume we only have 2 variables, x and y, and our model (in R code) is lm(y~x). Given that any 2 points can be used to form a line, I know it doesn't make much sense to try to fit this model if I only have 2 observations.
What about the case where I have 3 observations? Would this model pass the laugh test?
|
Possible Duplicate:
Probability of getting between
What is the probability that at least 24 of the next 50 people like to swim when the true probability of people liking to swim is 35%?
I thought it might be a conditional probability but I'm not really sure...
|
Consider two independent and identically distributed random vectors of dimensionality $N$, $\mathbf{x}$ and $\mathbf{y}$, where their elements are iid generated from a Gaussian with zero mean and variance equal to $\sigma^2$; i.e., $\mathbf{x} , \mathbf{y} \sim \mathcal{N}(0, \sigma^2)$.
What is the probability that $... |
I'm dealing with a homework.
We were given a software, with inputs, that we should measure and then verify that the time complexity is O(n^3).
I measured the software, picked best times from each batch (since that's the least affected one), and ended up with this:
304 70000
574 480000
775 1190000
850 1580000
10... |
Would like to understand primary reasons for making a data stationary?
I understand that a stationary time series is one whose mean and variance is constant over time. Can someone please explain why we have to make sure our data set is stationary before we can run different ARIMA or ARMA models on it?
Does this also ap... |
Suppose that we have a linear model $y_i = \beta_0 + \beta_1 x_i + \epsilon_i$ that meets all the standard regression (Gauss-Markov) assumptions. We are interested in $\theta = 1/\beta_1$.
Question 1: What assumptions are necessary for the distribution of $\hat{\theta}$ to be well defined? $\beta_1 \neq 0$ would be im... |
I'm currently setting up an experiment where we might want to do multiple comparisons (i.e. comparing several treatments with a control at the same time). It is pretty straightforward to calculate the needed sample-size using the Bonferroni correction. However, the Bonferroni method is pretty conservative, and I'm worr... |
I have a series of vectors, which are measurements from one sample at two time points.
First time point:
1.[5,3,2,4,4,3,6,5] (mean=4.000)
2.[5,6,3,3,4,3,4,5] (mean=4.125)
3.[6,3,4,2,5,3,5,7] (mean=4.375)
... etc.
grand mean=4.17
Second time point:
1.[1,2,1,2,1,3,4,5] (mean=2.375)
2.[2,2,3,1,1,3,3,5] (mean=2.500)
3.[1,3... |
I recently received this question from a student:
In a simple mediation model, if I have found the indirect effect (ab)
to be significant and the direct effect (c') to be small and
insignificant, does that mean I have full mediation or partial
mediation?
|
I need to process three data frames containing the same subgroups (name). So far I've been using this approach:
results = data.frame(name = factor("dummy"), col1 = 1, col = 2)
for( name in df1$name ) {
new.results = process(name, df1[df1$name == name, ], df2[df2$name == name,], df3[df3$name == name, ]
results = rb... |
I am trying to work on a process to improve how how well my team estimates. I want to look at using some statistics to help out and embrace the uncertainty in how we estimate tasks.
If I have a group of experts and I ask them for a best (b), average (a) and worst (w) case estimate for a task, creating a triangular dist... |
In a research article about sensitivity analysis of an ordinary differential equation model of a dynamic system, the author provided the distribution of a model parameter as Normal distribution (mean=1e-4, std=3e-5) truncated to the range [0.5e-4 1.5e-4]. He then uses samples from this truncated distribution for simul... |
I want to draw a plot in Matlab or Stata. I have a mean and CI for some distribution. there should be a line with the upper end of the line representing the upper CI and the lower end the lower CI and the middle, the average.
I am not sure how to do it or how to search for it. Can anyone kindly help me out ? Thanks.
NB... |
Given a distribution $f(x_i,y_i;\alpha,\beta)$ and joint probability function $F(x_1,...,x_N,y_1,...,y_N;\alpha, \beta)$
The first order derivatives are $\frac{\partial F}{\partial \alpha}$ and $\frac{\partial F}{\partial \beta}$
Is the first order condition
$\frac{\partial F}{\partial \alpha}=0$ and $\frac{\partia... |
Suppose we have two finite discrete probability distributions, say $A$ and $B$. For some event $e$ in both $A$ and $B$, $f_A(e) = \frac{P_A(e)}{P_A(e) + P_B(e)}$ and $f_B(e) = \frac{P_B(e)}{P_A(e) + P_B(e)}$. Does this have a name?
|
Is there a article/textbook that treats probability distributions on functions just like basic textbooks cover the classical distributions for scalar variables?
Suppose the random function $f$ has a gaussian process distribution with some mean function $m$ and covariance function $w$. I know how to generate random (fun... |
Possible Duplicate:
Fourier data with non-integer periods, correcting for phase bias
I have a not perfectly but quit periodic signal, with a length of only a few periods. What methods are available for automatically measuring its period?
I tried using the maximum of the Fourier transform, but this essentially only ... |
I'm using the Mann-Kendall function of the Kendall package in R to compute the statistics of the Mann-Kendall trend test of a huge time-series (19 millions elements). It has been running for 22 hours and it hasn't yet finished. Can you suggest a faster approach?
|
Can anyone explain how to compute the marginal effect of Probit and Logit model in layman's terms?
I am new to statistics and I am confused about these two models.
|
Can someone please tell me how to have R estimate the break point in a piecewise linear model (as a fixed or random parameter), when I also need to estimate other random effects?
I've included a toy example below that fits a hockey stick / broken stick regression with random slope variances and a random y-intercept va... |
Consider $Y_{ij} = \mu + u_i + e_{ij}$ where $\mu$ is a constant and $u_i ∼ N(0,\sigma_u^2
)$ is the subject $i$ random effect which is independent of the error term $e_{ij} ∼ N(0,σ_e^2)$. I can't figure out why $${\rm cov}(Y_{ij}, Y_{ik}) = \sigma_u^2$$
Can anyone please explain?
|
I'm just studying my statistics exams and I came across something odd.
When I try to get the 25th or 75th percentile with wolfram alpha, it gives me another answer than I should get according to my textbooks.
simple example: http://www.wolframalpha.com/input/?i=first+quartile+32%2C42%2C46%2C46%2C54
according to my text... |
I'm using naive bayes classifier to classify between two groups of data.
One group of the data is much larger than the other (above 4 times).
I'm using the prior probability of each group in the classifier.
The problem is that the result I get has 0% true positive rate and 0% false positive rate.
I got the same results... |
In practice, how to evaluate whether a AR(P) process is stationary or not?
How to determine the order for the AR and MA model?
|
I have 4 data sets, each with thousands of records/instances. There are 2 factors. One factor has 3 instances at each factor level (there are thousands of levels in the data set). The other factor also has thousands of levels, but with varying numbers of instances at each level. For each factor, I would like to mea... |
Any recommendations for choice of a constrained optimization library suitable for my optimization function? I am minimizing a i) non-linear function with linear equality and inequality constraints, and ii) have available the gradient and the hessian of the function.
If it helps, the function I am minimizing is the Kul... |
I have a sample that consists of 50 observations. The base model of the OLS-Regression with three control variables, two of them significant, has a $R^2=0.50$ and its F-Value is 7. Both –ovtest and –linktest (Stata 10.0) indicate no model misspecification.
I am testing four Hypotheses. However, after having included t... |
I am having difficulty finding information on the assumptions for the intraclass correlation. Can someone please tell me what they are?
|
What is the Likelihood function of a linear probability model?
I know the likelihood function is the joint probability density, but how to construct the likelihood function when we only have the probability $P(Y_i=1|X_i)$ and $P(Y_i=0|X_i)$?
|
I am looking for a viable method to create an alphabet out of multidimensional time series data. My intention is to use pattern/string matching algorithms (potentially genetic) to find profitable patterns.
Extra points if I can do this in R.
Any ideas?
|
I am using random forest on high-dimensional grouped data (50 numeric input variables) which have a hierachical structure. The data were collected with 6 replications at 30 positions of 70 different objects resulting in 12600 data points, which are not independent.
It seems random forest is over-fitting the data, si... |
I believe I have a very simple problem with missing data, but I'm a bit lost because all the materials I read seem to be focused on much more complicated cases.
I have a random variable $X$ which has a Binomial distribution with parameters $n$ and $p$ (i.e., $X\sim B(n,p)$), where $p$ is unknown ($n$ is known). I have ... |
Suppose I have two series of numbers and they don't have to be time series.
$S_1=$ {9,8,1 ...}
$S_2=$ {7,9,2 ...}
What are the methods to compare these two series and make a conclusion such that these two series are statistically similar, they have similar patterns or they are completely different?
I'm looking for patt... |
I've created a DLM (using the dlm package in R) with a linear trend (dlmModPoly(2)) and a seasonal component (dlmModSeas(seasons)). After filtering, the residuals look Gaussian according to a qqplot. The confidence band around the estimates looks very good as well.
However, the acf plot of the residuals shows definite ... |
I’m working on a data set in order to evaluate the impact of drying on sediment microbial activities. The objective is to determine if the impact of drying varies among sediment types and/or depth within the sediment.
The experimental design is as follows:
The first factor Sediment corresponds to three types of sedimen... |
I've been reading about generalised additive models. I've been using this data (which is a reformatted version of data from Hastie's website), and running my code in R. This data essentially consists of whether a patient has or does not have coronary heart disease (the variable to be modelled) and several patient char... |
Why would one use age and age-squared as covariates in a genetic association study? I can understand the use of age if it has been identified as a significant covariate, but I am at a loss as to the use of age-squared.
|
I have a simple question for you guys but I am studying for exams and I honestly forgot how this was done.
Here is the problem:
"A vase contains 4 white marbles, 3 red and 2 green. You draw marbles
2 without putting the first one back after the second.
What are the chances that you draw a red marble after the first ... |
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