Linked Questions

20
votes
3answers
17k views

What tests do I use to confirm that residuals are normally distributed?

I have some data which looks from plotting a graph of residuals vs time almost normal but I want to be sure. How can I test for normality of error residuals?
55
votes
10answers
3k views

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' ...
3
votes
1answer
203 views

KS test for normality on residuals from OLS vs. MLE

This is a conceptual issue. Suppose, one wants to test the residuals $e_t$ from the regression for normality. So, he runs the regression, obtains the estimates of error variance $\sigma^2$, and forms ...
25
votes
5answers
5k views

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 ...
0
votes
1answer
30 views

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 ...
0
votes
1answer
31 views

Normality Tests in samples with outliers

I'm making a code in R that contains some parametric and non-parametric tests, like ANOVA and Kruskal-Wallis. To know if I should use one or another I check the "normality" of the test sample. My ...
30
votes
2answers
98k views

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?
0
votes
1answer
33 views

Quasi-Poisson - Goodness of fit

Can I use likelihood ratio chi-squared tests to test the goodness of fit for quasi-Poisson models?
0
votes
3answers
84 views

How can I check if my data-frame is normally distributed in R?

I have a data frame with 7 columns that holds numerical and integer values where some columns, even though numerical, are binary values (e.g. a dummy variable for sex; $0=\text{male}$, $1=\text{female}...
10
votes
2answers
15k views

“Ties should not be present” in one-sample Kolmgorov-Smirnov test in R

I am going to use the Kolmogorov-Smirnov test to test normality of MYDATA in R. This is an example of what I do ks.test(MYDATA,"pnorm",mean(MYDATA),sd(MYDATA)) ...
2
votes
2answers
322 views

Comparing mean difference between groups where raw data follows a long tail distribution

I am trying to determine if there is a mean difference between two test groups. The raw data (continuous scores) is distributed according to a long tail distribution. Each test group has more than ...
1
vote
2answers
57 views

Normality testing with very large sample size

Hypothesis testing such as Anderson-Darling or Shapiro-Wilk's test check normality of a distribution. However, if the sample size is very large, the test is extremely "accurate" but practically ...
1
vote
2answers
231 views

Tests of normality - qq and Shapiro-Wilk

I am new to the world of stats... My data had a log normal distribution, so transformed by log to get it nearer normal distribution. This is real-world data. From here I want to establish if my data ...
3
votes
2answers
75 views

When, if ever, should a normality test be performed on real-world data?

I've recently come across some research studies and internal reports from my company where multiple mean-comparison tests are performed. The procedure is often as follows: first, the data is checked ...
2
votes
3answers
85 views

Not convinced about normality based on QQ plot, Shapiro and KS $p <0.001$

I have about 1000 data points, I'm trying to run a $t$-test because my points are divided in 2 groups and I want to compare them. The results of Shapiro-Wilk normality test: ...

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