Tagged Questions

36 views

What does a p value of 0.7447 in an F test mean? [duplicate]

I have used R to try to discern differences between male and female students and their preferences for chocolate. My data is not normally distributed, and data transformations failed to 'squash' the ...
58 views

In hypothesis testing, does a p-value less than alpha always mean you reject NH?

I have learned that a p-value that is less than alpha means you reject the null hypothesis. But this seems to only make sense in the case of lower tail tests. What do you do for upper tail tests?
97 views

Three important issues

I don't understand three important issues : (1) Why do we calculate the test statistic under the null hypothesis ? (2) Why do we reject the null hypothesis when : p-value < significance level ? ...
59 views

How to correctly compute p-value for hypothesis test?

Let the random variable X represent the amount of money carried by a student in class. To determine μ , the mean amount of money carried by a student, an experiment was conducted in class. The class ...
95 views

Combining p-values from different statistical tests applied on the same data

Although the title of the question appears trivial, I would like to explain that it is not that trivial in the sense that it's different from the question of applying the same statistical test in ...
145 views

When does it make sense to reject/accept an hypothesis?

In To P or not to P: on the evidential nature of P-values and their place in scientic inference, Michael Lew has shown that, at least for the t-test, the one-sided p-value and sample size can be ...
157 views

p-value of hypothesis “a home court advantage exists”

The practical POV: I sample 35 matches: 15 turn out as home win, 10 as tie and 10 as home lose. I want to conduct a test for the hypothesis "A home court advantage does exist." with a significance ...
64 views

Statistical significance in canonical correlation analysis

I do canonical correlation analysis between two multivariate datasets $X$ and $Y$. For each pair of canonical variates (x-y pair) I get the canonical correlation coefficient. How can I test its ...
36 views

Is this test answer good enough to show Granger Causality?

I used an inbuilt Matlab function to check for Granger Causality between two time series P and T that have a correlation coefficient of 0.6. The function is : ...
132 views

What is the best way to analyze data if your experimental design changes while running the experiment?

I imagine this is a somewhat common situation in practice. I am thinking mainly in terms of preclinical drug trials. 1) During the course of the study a new technique is learned or some time/money is ...
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Is p-value involved in Neyman-Pearson Testing procedure?

It seems to me that, after having a predetermined level of significance, the Neyman-Pearson approach only requires to see if the observed x lies in the rejection region or not. In this case, how to ...
139 views

Avoiding p-values and reporting t-values instead. References?

I was wondering if I could get some opinions on an issue. I'm analyzing my data using mixed-effects modeling in R (lme4 package). My model has by-subject and by-item intercepts and slopes, and random ...
91 views

Paper on performing hypothesis tests based on outcome of another test

It is well known that it is problematic to choose a statistical test based on the outcome of another statistical test, as the p-values are difficult to impossible to interpret (e.g. Choosing a ...
60 views

How to analyze and interpret A/B test results via Bootstrap method?

First of all, apologies if this is a stupid question, I'm fairly new to statistics, so still finding my way a bit in terms of the fundamentals! We've run a split test of a new product feature and ...
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Can you use the paired t-test in what seems like an unpaired t-test situation?

I came across a situation where a large retailer is testing a new retail program. It selected specific pilot retail stores to test this program. Next, it selected a control group of retail stores so ...
52 views

How to use ks test for 2 vectors of scores in python?

I am trying to figure out how to determine whether to reject or not the null hypothesis using ks-test. In matlab there is a function named kstest2 decides if it should reject $H_0$. I want to use ...
84 views

Cumulative distribution of p-value

Say I have multiple tests on N data points, for each I get a p-value ($0 < p < 1$). If the null hypothesis is true, I would expect that the distribution of p-value to be uniform. If, however the ...
148 views

What are Hommel Hochberg corrections?

I have recently been introduced to to Hommel Hochberg corrections. I am trying to find a simple explanation about what this actually is/does, but am having no luck. Can anyone please give a brief and ...
50 views

$p$ value for a randomized test

For a randomized test, how do we compute the $p$-value? For example, suppose the test is of the form: $\phi(X)=1$ if $X > c$, $\phi(X)=p$ when $X=c$ and $\phi(X)=0$ otherwise. How do we compute the ...
61 views

Statistical significance problem

I've got an algorithm which assigns a score to a list of individuals (nodes). I want to discover which nodes received a statistically significant score. So I "randomized" the algorithm in order to ...
170 views

Kendall Tau-b correlation coefficient becomes more significant with many additional ties

Say I have two vectors of length N, x = [1, 10, 12, ..., 5, 6] y = [2, 11, 10, ..., 7, 9] I compute the Kendall tau-b rank order correlation on these two vectors ...
57 views

Who decided that p value should be less than 0.05 and why? [duplicate]

In many scientific fields, a p value less than 0.05 is considered significant, pointing to real difference in reality, whereas anything above it cannot be accepted (i.e. null hypothesis cannot be ...
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Understanding why p value is uniformly distributed [duplicate]

I know that the mathematically, p values should be uniformly distributed under the null hypothesis. However, what is this null hypothesis (in this context)? Can someone give me an example please ?
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Computing P-value

I am doing a lower-tail test and my z-statistic is -1.57. Now I have to calculate the p-value. My way of finding the p-value using a z-table is: I looked for row -1.5, then look for column 0.07. The ...
230 views

Stouffer's Z-score method: what if we sum Z^2 instead of Z?

I am performing $N$ independent statistical tests with the same null hypothesis, and would like to combine the results into one p-value. After some googling it seems to me that there are two ...
154 views

Estimating p-value of a very rare event using Monte Carlo

I am doing a Monte Carlo sampling from the null hypothesis in order to estimate a p-value of my data. Normally I would do, say, 1000 Monte Carlo runs, count the number of runs where I get values of my ...
91 views

P-values and null hypothesis

I am making a study guide for a statistics test at the end of the summer semester. My professor went through some stuff that will be on the test. There is one type of question that I just don't ...
106 views

Is there a sample distribution so that the distribution of p-value is skewed towards 1?

I heard that: Under a null distribution, the distribution of p-value is flat over $[0,1]$. Under an alternative distribution, the distribution of p-value is skewed towards $0$. Is there a sample ...
105 views

Intuitive explanation of why p is not the probability of the null hypothesis [duplicate]

I've got to teach a basic course on the $\chi^2$ test soon, and I will of course insist on the fact that $p$ is not the probability of the null hypothesis to be true, and that the result of the test ...
77 views

How to make a one-sided test for proportion in R

I've to make some tests for proportions in R because of some A/B duties. I know that given s1, sc the number of success of two samples and n1, nc the total number of experiments, I can do this for H0: ...
184 views

What would be the logical inverse of a hypothesis test? (If any)

I just thought I'd ask this question to see if there is a method or reasoning of proving a hypothesis test inversely, whilst logic remains the same. I will use the following example, which I recently ...
626 views

Can p-values for Pearson's correlation test be computed just from correlation coefficient and sample size?

Background: I read one article where authors report Pearson correlation 0.754 from sample size 878. Resulting p-value for correlation test is "two star" significant (i.e. p < 0.01). However, I ...
390 views

Is a p-value of 0.04993 enough to reject null hypothesis?

In a Wilcoxon signed-ranks statistical significance test, we came across some data that produces a $p$-value of $0.04993$. With a threshold of $p < 0.05$, is this result enough to reject the null ...
915 views

“Accept null hypothesis” or “fail to reject the null hypothesis”?

I'm trying to conduct a Student's t-test for a table of values while trying to follow the explanation and details found on this website. I understand that if the p-value is <.01 then it's really ...
125 views

q-value and p-value

I have heard about q-values, in lines of p-values. What is the main benefit of using q-values over p-values? Why is it that p-values have to be adjusted? Wikipedia only has two lines of mention as ...
588 views

Another p-value fallacy

Wikipedia examples say that a coin is unfair if it generates a sequence 1111111. A high alternation rate, such as 1010101010, would be similarly unfair. What is a fallacy to think that a coin is ...
47 views

Is the p-value still uniformly distributed when the null hypothesis is composite?

When the null hypothesis is simple (i.e., has only distribution of the sample) and the only distribution of the sample is continuous, the p-value can be shown to be uniformly distributed over (0,1). ...
288 views

Ratios of means - statistical comparison test using Fieller's theorem?

I would really appreciate any suggestions with the following data analysis issue. Please read till the end as the problem at first may appear trivial, but after much researching, I assure you it is ...
46 views

Is the p-postulate true?

The p-postulate is the notion that equal p-values provide equal evidence against the null hypothesis. Royall, R. N. (1986). The Effect of Sample Size on the Meaning of Significance Tests, The ...
76 views

Hypothesis Testing

A Lab has been asked to evaluate the claim that drinking water in a local restaurant has a lead concentration of 6 parts per billion (ppb). Repeated measurements follow a normal distribution ...
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Regarding p-values, why 1% and 5%? Why not 6% or 10%?

Regarding p-values, I am wondering why 1% and 5% seem to be the gold standard for "statistical significance". Why not other values, like 6% or 10%? Is there a fundamental mathematical reason for ...
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Can significant relationship be used with significant difference at same time?

Usually I read about either testing for significant relationship or significant difference but can they used both to prove something? For example, assume a shop wants to compare its profits per month ...
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How to prove that the east teams are higher in the ranking that west or vise vera?

If we want to compare the rankings of teams that are from east or west, how can we show that east or west have higher rankings than other? Example ...
240 views

Samples that will result in a large p-value

Consider a one-sample t-test regarding the population mean time to complete a task with a one-sided alternative hypothesis of Ha: μ < 10 minutes. A random sample of times to complete the ...
458 views

R linear regression test hypothesis for zero slope

I'm working with some data and I used R to the a linear regression model Y = aX + b. The code I used was summary(lm(Y~X)) What I ...