246 questions linked to/from Is normality testing 'essentially useless'?
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### Normality test and Outlier detection [duplicate]

In this question, I would like to ask two things: outlier detection normality test Details are as follows: I need to detect and remove outliers in my data. Before doing that, I want to test if my ...
600 views

### Fitting data to a log-normal distribution [duplicate]

For a simulation study I've been trying to find an appropriate distribution for job handling times in R. I have a very large dataset of 77010 records (handling time in seconds). I've been exploring ...
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### Is the practice of doing normality test before doing t test wrong? [duplicate]

When I read research papers, I saw that many people do a normality test first, then decide if a t-test or a non-parametric test should be applied. I have a concern about such practice. Let’s say the ...
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### Why according to distribution graph it's normally distributed, but Jarque-Bera test shows non-normally distributed? [duplicate]

I am working on Kaggle's house pricing exercise and I cannot understand something. I watch and read articles on normality tests, and more specifically JB test, but I cannot understand why according to ...
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### Is it possible to test for a Gaussian distribution? [duplicate]

Suppose that I have $n$ independent samples from a probability distribution. I believe that the distribution is Gaussian ($G$) but I don't know; then my question is: does there exist a test such that ...
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### What is exactly the non-normality requisite for nonparametric tests? [duplicate]

As the title says, what is exactly what is being tested before deciding to use a non-parametric alternative test (as Kruskal-Wallis for ANOVA, or Mann-Whitney's U for student's t)? Most sources are ...
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### Normality test with p-value equal to zero [duplicate]

I have an array dataset of about 650.000 points. I want to test if the dataset follow a normal distribution or any other distribution. The first thing I did was to split the data in groups, find the ...
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### How to verify assumptions of a normal distribution? [duplicate]

I'm working with the iris data.I made a density plot And a qq plot For sepal Length.It looks Approximately normal With the left skew And a flat peak The points In the qq Plot Stay within The ...
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### If the data is not normally distributed and the skewness is = 0.208 SE of skewness is 0.144 , is it acceptable to use t-test? [duplicate]

The sample size is 288 and by Shapiro- Wilk test the data is not normally distributed.
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### Usefulness of rejecting null in normality test [duplicate]

In this Stackoverflow answer Ian Fellows said, Normality tests don't do what most think they do. Shapiro's test, Anderson Darling, and others are null hypothesis tests AGAINST the the ...
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### testing normality for a two way anova, residuals as well as each sample? [duplicate]

to test a two way ANOVA do you have to test each sample for normality as well as normality for the residuals?
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### What are common statistical sins?

I'm a grad student in psychology, and as I pursue more and more independent studies in statistics, I am increasingly amazed by the inadequacy of my formal training. Both personal and second hand ...
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### Are large data sets inappropriate for hypothesis testing?

In a recent article of Amstat News, the authors (Mark van der Laan and Sherri Rose) stated that "We know that for large enough sample sizes, every study—including ones in which the null hypothesis of ...
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### T-test for non normal when N>50?

Long ago I learnt that normal distribution was necessary to use a two sample T-test. Today a colleague told me that she learnt that for N>50 normal distribution was not necessary. Is that true? If ...
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### How to choose between t-test or non-parametric test e.g. Wilcoxon in small samples

Certain hypotheses can be tested using Student's t-test (maybe using Welch's correction for unequal variances in the two-sample case), or by a non-parametric test like the Wilcoxon paired signed rank ...
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### What are some examples of anachronistic practices in statistics?

I am referring to practices that still maintain their presence, even though the problems (usually computational) they were designed to cope with have been mostly solved. For example, Yates' ...
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### When to use simulations?

So this is a very simple and basic question. However, when I was in school, I paid very little attention to the whole concept of simulations in class and that's left me a little terrified of that ...
215k views

### How to perform a test using R to see if data follows normal distribution

I have a data set with following structure: a word | number of occurrence of a word in a document | a document id How can I perform a test for normal ...
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### Is a distribution that is normal, but highly skewed, considered Gaussian?

I have this question: What do you think the distribution of time spent per day on YouTube looks like? My answer is that it is probably normally distributed and highly left skewed. I expect there is ...
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### Regression when the OLS residuals are not normally distributed

There are several threads on this site discussing how to determine if the OLS residuals are asymptotically normally distributed. Another way to evaluate the normality of the residuals with R code is ...
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### Distribution hypothesis testing - what is the point of doing it if you can't “accept” your null hypothesis?

Various hypothesis tests, such as the $\chi^{2}$ GOF test, Kolmogorov-Smirnov, Anderson-Darling, etc., follow this basic format: $H_0$: The data follow the given distribution. $H_1$: The data do not ...
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### Appropriate normality tests for small samples

So far, I've been using the Shapiro-Wilk statistic in order to test normality assumptions in small samples. Could you please recommend another technique?
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### Test for finite variance?

Is it possible to test for finiteness (or existence) of the variance of a random variable given a sample? As a null, either {the variance exists and is finite} or {the variance does not exist/is ...
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### When does Fisher's “go get more data” approach make sense?

Quoting gung's great answer Allegedly, a researcher once approached Fisher with 'non-significant' results, asking him what he should do, and Fisher said, 'go get more data'. From a Neyman-Pearson ...
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### Is it meaningful to test for normality with a very small sample size (e.g., n = 6)?

I have a sample size of 6. In such a case, does it make sense to test for normality using the Kolmogorov-Smirnov test? I used SPSS. I have a very small sample size because it takes time to get each. ...
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### My distribution is normal; Kolmogorov-Smirnov test doesn't agree

I have a problem with the normality of some data I have: I've done a Kolmogorov test which says it isn't normal with p=.0000, I don't understand: the skewness of my distribution =-.497, and the ...
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### How is Poisson distribution different to normal distribution?

I have generated a vector which has a Poisson distribution, as follows: x = rpois(1000,10) If I make a histogram using hist(x)...
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### What is the difference between the Shapiro-Wilk test of normality and the Kolmogorov-Smirnov test of normality?

What is the difference between the Shapiro-Wilk test of normality and the Kolmogorov-Smirnov test of normality? When will results from these two methods differ?