Linked Questions

0 votes
1 answer

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 ...
valerie's user avatar
  • 26
0 votes
1 answer

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 ...
mat's user avatar
  • 699
1 vote
0 answers

Normality assumption check on separate groups vs. on residuals [duplicate]

I was taught in applied stats to verify the assumption of normality on my variables separated by group. For example, if I'm studying a continuous variable like weight (g) in two groups of subjects: A ...
BioLeal's user avatar
  • 115
1 vote
0 answers

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 ...
David Chin's user avatar
0 votes
0 answers

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 ...
Sam's user avatar
  • 1
0 votes
0 answers

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 ...
upendra's user avatar
  • 145
371 votes
15 answers

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 ...
shabbychef's user avatar
  • 14.2k
138 votes
3 answers

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 ...
MarkDollar's user avatar
  • 5,785
59 votes
3 answers

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 ...
Roman Luštrik's user avatar
20 votes
3 answers

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?
pb1's user avatar
  • 201
2 votes
4 answers

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 ...
pamela's user avatar
  • 21
9 votes
2 answers

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 ...
DeanP's user avatar
  • 871
7 votes
2 answers

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 ...
evdstat's user avatar
  • 591
4 votes
2 answers

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 ...
Cesare Camestre's user avatar
13 votes
2 answers

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 ...
Psychokwak's user avatar

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