Linked Questions

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votes
1answer
520 views

We said the data is normally distributed, based on the raw data or residual? [duplicate]

I have a confusing regarding the assumption test for the data, in some theory were said that there are three assumption of data as we called as "good" data: Independent Normally distributed ...
0
votes
1answer
133 views

Why is Normal Distribution required to perform an independent t-test? [duplicate]

I've been told many times that, when carrying an independent t-test, I have to determine whether my dependent variable (DP) is normally distributed on boths levels of my independent variable (IV). On ...
1
vote
0answers
39 views

Non-Normal data in multiple linear regression [duplicate]

My study involve 73 subject. I want to carry out a multiple linear regression in order to form a predicting formula. However my dependent variable is not normally distributed according to a normality ...
0
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0answers
24 views

Can I do a factorial ANOVA on non-normal data? [duplicate]

If I am comparing the effect of age, sex, location (numerical) on various numerical parameters, but one of these responses are not normally distributed, can I still do a factorial ANOVA? I can't do a ...
0
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0answers
19 views

how to transform non-normal data for downstream statistical analyses [duplicate]

I have a dataset that look at the effect on photosynthesis and respiration. When i checked to see if the data looks normal or not, i find that for both the variables the distributio is non-normal. In ...
339
votes
16answers
120k views

Is normality testing 'essentially useless'?

A former colleague once argued to me as follows: We usually apply normality tests to the results of processes that, under the null, generate random variables that are only asymptotically or ...
130
votes
3answers
41k views

What if residuals are normally distributed, but y is not?

I've got a weird question. Assume that you have a small sample where the dependent variable that you're going to analyze with a simple linear model is highly left skewed. Thus you assume that $u$ is ...
55
votes
3answers
239k views

ANOVA assumption normality/normal distribution of residuals

The Wikipedia page on ANOVA lists three assumptions, namely: Independence of cases – this is an assumption of the model that simplifies the statistical analysis. Normality – the distributions of the ...
20
votes
3answers
20k 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?
8
votes
2answers
9k views

Normality of residuals vs sample data; what about t-tests?

An addition to the common confusion about normality testing in inferential statistics for general linear models: I understand the assumption of normality refers to the residuals in ANOVA and ...
1
vote
4answers
8k views

Assessing normality of distribution

I'm having trouble understanding how to assess normality for discrete data. I understand the the K-S test is available to test the normality distribution for continuous data. However, what would be ...
7
votes
2answers
9k views

Testing normality

I have a large dataset (500000 data, V1 column include all the data). x <- read.csv("mydata.csv", header=F) hist(x) Which gives: Looking at the data, I ...
3
votes
2answers
3k views

Mboxcox, interpreting difficult regressions

Mboxcox in Stata suggests transforming my variables using a power of 0.1 for the independent variable, and 0.4 for the dependent variable. I have run the model, and it fixes problems associated with ...
12
votes
2answers
499 views

Why some people test regression-like model assumptions on their raw data and other people test them on the residual?

I am a Phd Student in experimental psychology and I try hard to improve my skills and knowledge about how to analyze my data. Until my 5th year in Psychology, I thought that the regression-like ...
1
vote
2answers
15k views

What to do when Kolmogorov-Smirnov test is significant for residuals of parametric test but skewness and kurtosis look normal?

I have conducted a parametric test in a study, n=290. I want to assess whether the residuals of this test are normally distributed. The skewness and kurtosis of the residuals are -0.017 and -0.438 ...

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