In hypothesis testing, the $p$-value refers to the probability of seeing a result as extreme (or more so) than the one observed, given that the null hypothesis is true. When the $p$-value is small, then there is good evidence that the null hypothesis is false, since it would make the observed data ...

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What is p-value in correlation? Can you have a one-sided correlation?

Let's say you have data from two random variables $X$ and $Y$, and the two random variables are highly correlated (ex: $r=.97$). The p-value, which is testing the null hypothesis that there is no ...
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19 views

Does rejection of null hypothesis ($p < \alpha$) for one representative sample imply rejection in a different sample?

I am new to hypothesis testing so forgive me if this has already been asked. Suppose that I've already decided on a null hypothesis with a significance level $\alpha = 0.05$, then obtained my ...
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32 views

How to use an optimization solver to get t-stats and p-values for the estimates?

I calculate a data log likelihood (evaluated at a set of parameters to be estimated), and my task is to find the set of parameters that maximize my log likelihood. My problem is: thought there are a ...
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8 views

Statistical Comparison of two different waves

I have two waves data for a couple of cities and I need a comparison W I W II City A 10,000 10,100 City B 200 202 City C 1500 1515 There is a 10% increase of ...
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224 views

Statistically significant?

I am new to statistics and so any help would be greatly appreciated! I have done a study looking at the number of samples being sent to the lab for patients with UTIs in a GP practice. I then ...
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15 views

How is p-value performing as a measure of association?

It's known that Cramér's V (Chisq adjusted for table dimension and sample size) is a good measure of strength association. But what about the p-value? P-value (as a probability of the numbers we have ...
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28 views

How should I interpret a Spearman's rank correlation significance of zero?

This is a follow up to a Stack Overflow question I'm calculating the Spearman rank correlation coefficient between two vectors using corr in Matlab. The two ...
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352 views

Still confused with the p-value definition

The p-value is defined as the probability, under the assumption of the null hypothesis H, of obtaining a result equal to or more extreme than what was actually observed. A p-value lower ...
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8 views

Compute a Pvalue from the averaged Pearson and Spearman rho

on the one hand, Pearson correlation is sensitive to outliers, while Spearman is not. On the other hand, if you have quantitative data, Spearman will treat it like ordinal data. How about averaging ...
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13 views

Expected p-values from a series of trials

I'm looking at this toxicology study (http://www.sciencedirect.com/science/article/pii/S0041008X1500085X). The study has a negative control group, a positive control group and three treatment groups ...
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1answer
58 views

No significant tests when using Benjamini-Yekutieli multiple testing correction on millions of tests

I am using a univariate filter to reduce the number of features prior to applying a learning algorithm to a huge binary classification dataset (22510066 features x 500 examples). All the features are ...
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1answer
15 views

Obtaining test statistic for problem with two populations

Given a sample population of 54 men and 61 women, I want to figure out whether or not the average male spends less time during his daily shower than the average female spends during hers. The average ...
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44 views

P values of coefficients in rlm robust regression

I am using rlm robust linear regression of MASS package on modified iris data set as follows: ...
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12 views

Hypothesis testing: 95% confidence intervals of group means overlapping zero or 83% confidence intervals?

I am trying to select between the following two methods to look for significant differences between two abundance estimates: 1) calculation of the 95% confidence interval for the difference between ...
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19 views

Standard multiple regression and multiple dependent variables. and bonferroni correction?

I have a question regarding running multiple regression equations with multiple dependent variables. Three independent variables and 3 dependent variables. A colleague advised me to conduct three ...
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1answer
52 views

Help with HW questions

I have two following questions I could not really decipher how to get the P-Value. Data from a recent year showed that 71% of the tens of thousands of applicants to a certain program were accepted. ...
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16 views

p-test for parameter

Statisticians, number magicians, I was wondering what the best way is to check for the equality of two parameters including possibly a confidence interval and p-value. $$H_0:\beta_1=\beta_2\vert\ ...
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25 views

multiple hypothesis correction for meta-analysis with missing p-values

I would like to combine multiple p-values (e.g., using Fisher or Stouffer), where some hypotheses may have missing p-values across studies. e.g., ...
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1answer
84 views

p-value in odds ratio and regression

I have a few questions about the p-value. Firstly: Let's say we have a p-value of 0.52 in a contingency table analysis with a sample size of 60. If the sample size would be 90 with the same sample ...
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1answer
49 views

Statistical test for the difference in center positions of two receptive fields

I am a neuroscientist, and have neuronal response measurements for a large range of stimuli delivered to my subjects. I use this data to construct receptive fields (RFs), which show the mean response ...
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2answers
29 views

Calculating P- value

In ANOVA table , I got $F$-statistic $=330.285$ degrees of freedom (df) due to regression $= 6$ Error degrees of freedom $= 9$ But i don't know how to calculate $p-$value ? I have tried in ...
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13 views

How to find significance when performing many significance tests

I have 4 Likert scales in both a pre- and post-survey. Each scale shows significant change from pre to post. I'd like to identify which individual items have a significant change as well. There are ...
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1answer
137 views

Why are all my p-values so low in logistic regression model?

I'm trying to make a regression model to explain a dependent variable that follows a binomial distribution - I have data on the number of successes and the number of trials for each observation. The ...
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26 views

Correction of P value for correlation matrix

If one has to perform correlation matrix, correction for multiple testing is likely to be useful. If significant P value is taken as (0.05/number_of_variables) (e.g. for 50 variables, 0.05/50 = ...
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52 views

Relative size of p value at different sample sizes BUT same odds ratio

Will the relative size of the p-value increase or decrease with the increase of sample size? My guess is that it will decrease, however, would it be the same case if they both have the same odds ratio ...
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32 views

A/B Testing - Can you trust the math with small samples?

Let's say I test a new version of my signup page. After the original and the variant each get 100 views, here are my results: Original had 1 conversion (1%), and a 95% confidence interval of 0-2.95% ...
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90 views

I understand P-value but I am not sure about this question

What probability indicates the p-value? (more than one answer possible) a: The probability of a type I error. b: The probability of a type II error. c: The probability of rejecting the alternative ...
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13 views

May I mix pvalues from ANOVA with pvalues from Kruskal-Wallis test?

I am studying one-way Analysis of Variance (ANOVA) from this book. Suppose I want to run one-way ANOVA on multiple sets of observations. For instance, I have a matrix of $n$ features and $m$ ...
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Comparison of two datasets with different variables

I am going to explain my problem as simple as I can. I have two sequences of DNA (two different datasets). Each sequence has three different variables or factors (for biologists: Hi-C, Chip-seq and ...
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38 views

Use lmer to test main effects and interaction

I have to solve a problem using a linear mixed model (lmer). Six subjects performed two tests, (test1, ...
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76 views

Test two groups with only sample statistics or without distributional assumptions

I have two sets of samples, A and B. I want to find whether the underlying mean (i.e. if the sample size was infinite) of A is greater than that of B, to a certain confidence (95%). There are two ...
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32 views

p-value and sample size [closed]

What would be the the p-value for a $\chi^2$ test when $n = 90$ when the p-value is .052 for $n = 60$?
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38 views

Slope analysis where one group is not normally distributed

I am currently doing analysis of five separate drug groups and their changes in levels of prescription over time. Having done linear regression on excel I am comparing the 'steepness' (m) of the ...
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1answer
75 views

Likelihood ratio tests using ML vs. REML

I am using Mixed effects models (nlme package in R) to choose the model with the best random and fixed effects. I am following the procedure of Zurr et al. (2009) ...
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1answer
34 views

Closed form solution for t-stats and p-values in multiple regression

I am trying to build a spreadsheet that will perform multiple linear regressions on a number of data series using the closed-form solution. It was fairly straightforward to write the solution for the ...
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Confusion with false discovery rate and multiple testing

I have read this great paper by David Colquhoun: An investigation of the false discovery rate and the misinterpretation of p-values (2014). In essence, he explains why false discovery rate (FDR) can ...
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1answer
154 views

how to calculate a p-value for a null hypothesis given a z-score

I'm new to statistics and would love help with the following: Given an iid sample $X_1,...,X_{10}$ assume that $X_i\sim N(\mu,5)$. using the one-sample test we got a z-score of $2.2$. How do I ...
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38 views

Question related to p-value

when I read Casella's Statistical Inference, the exercise 8.51 is: where (8.3.9) is $p(x)=\sup_{\theta\in\Theta_0}P_\theta(W(X)\geq W(x))$, and $W(X)$ is a statistic s.t. the large values give ...
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The abundance of P values in absence of a hypothesis

I'm into epidemiology. I'm not a statician but I try to perform the analyses myself, although I often encounter difficulties. I did my first analysis some 2 years ago. P values were included ...
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26 views

Large samples and the p-values almost zero in GEE models

I’m trying to find correlations between some environmental variables and a binary variable, berried/not berried females (rock lobster). I have 20 years of data that were sampled on a daily basis, ...
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1answer
64 views

simulate t-tests of mean differences

I would like to simulate t-tests of mean differences. I would like to simulate data based on 1) pre-specified (desired) mean difference between the variables and 2) desired t value 3) and p-value ...
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145 views

Goodness of fit chi-square test for a number of PCA components

I have been trying to carry out Principal Component Analysis (PCA) in R using the function psych::principal. However the returned $p$-value has been very low in ...
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26 views

Calculate Unpaired Welch-test p-value from 2 data sets

I am trying to calculate p-values from any two sets of numbers. I use Welch's t-statistic for sets 1 and 2, where $\bar{x}_a$ is the mean for set $a$, $\sigma^2_a$: is the variance for set $a$, and ...
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1answer
37 views

Understanding Bartlett's test from SAS

I am trying interpret the results of Bartlett's test run in SAS. This is the output I get: ...
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43 views

Can p-value = <0.05 with CI that includes 0 using chi2 in Stata?

I am doing a pretty straightforward analysis in Stata comparing proportions of respondents in 2 groups (in this case, rural vs. urban) who agree with different questions on a survey. For one of the ...
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1answer
79 views

Effect of sample size in F-test?

Having worked hard to understand the t-test, I'm rapidly falling out of love with it. All that is required in the t-test to gain significance is increase sample size, which renders it close to ...
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15 views

Post-hoc test on 3 groups comparison

I have 3 groups each with 6 values. After performing acceptable levene test for Homogeneity of Variance, I performed Anova on my data. It was significant, and I started to perform post-hoc test. The ...
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1answer
31 views

Strange two sample z test result in experiment

I performed an experiment on a virtual population wanting to see whether Vitamin C can positively affect performance on an IQ test. I gathered 80 people and grouped them into two groups of 40. ...
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70 views

Are different p-values for chi-squared and z test expected for testing difference in proportions?

I'm trying to test the difference in proportions using the z test method and chi-squared method, but am getting very different answers. Is that normal? My data: ...
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121 views

How much of your p-value do you report in a publication? [duplicate]

I know this will vary from journal to journal, but I'm working on my first publication and have had little guidance, so any personal experiences would be helpful to me. When you present your p-values ...