Normality test [Simply Explained]

One of the most common requirements for statistical test procedures is that the data used must be normally distributed. For example, if a t-test or an ANOVA is to be calculated, it must first be tested whether the data or variables are normally distributed. This is done with a test of normality.

If the normal distribution of the data is not given, the above procedures cannot be used and the non-parametric tests, which do not require normal distribution of the data, must be used.

How do I test normal distribution?
Normal distribution can be tested either analytically or graphically. The most common analytical tests to check data for normal distribution are the:
1) Kolmogorov-Smirnov Test
2) Shapiro-Wilk Test
3) Anderson-Darling Test
For the graphical test either a histogram or the Q-Q plot is used. Q-Q stands for Quantile Quantile Plot, it compares the actual observed distribution and the expected theoretical distribution.

Normality test

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[ganesh-]

00:02 The video explains testing for normality.
01:00 Normality tests check if data fits a normal distribution
01:56 P-value and normal distribution
02:50 Normality tests help to check distribution types
03:52 Large sample size can lead to rejecting the assumption of normal distribution based on small p-values.
04:53 Use QQ plot for better assessment of normality
05:49 Using data tab for testing normal distribution
06:52 Understanding the importance of normality test in data analysis
Crafted by Merlin AI.

[hamidD]

Can I ask a question about normal distribution as part of the assumptions in ANOVA please? Are we looking at normal distribution for the whole set of data or for each independent variable group?
Say we're doing a one way ANOVA without repeated measures and we have 3 groups (A, B, C) who had one dependent variable measure (weight). Should we run normality test for each of A, B, and C ?
Thank you

[khalidfatni]

Such a life saver explanation 😍❤
Thanks a lot.

[rhondaallen]

Great explanation on Normal Distribution!

[mossmoss]

youre better than my teacher omg thank you

[shimelisdekeba]

Very nice explanation you have done with DATAtab. I need to know how it can be done in Excel sheet.

[Poonams]

What to do when normality test is positive for one parameter and negative for other parameter .

[siddhantchatterjee]

What are the two visual methods that the presenter mentions?

[eltlisteningtasks]

What is the degree of freedom in Shapiro-Wilk test ?

[shitejw]

i have question. i have done 2 research hyphotheis and their normaality tests.For eg i have said ho the perceivness . bout social media follows normal and h1 follows not normal.My test shows both my objectives are not normally distributed .so how to interprete in disccussion chapter and conlunsion

[roguecats]

Instead of obtained score can normal distribution test be applied on likert response?

[aminaabdulmelik]

We should do this for all kind of study like crosectional study?

[amogh]

For data that is collected in a Likert Scale, won't the data always violate the normality assumption? Because, the likert scale takes discrete values.

[abdul_raheemshahzad]

wow mam well explaniation about normalilty test, but I have question that for analitical method we have a threshold of 0.05 i.e if results are less than 0.05 we can say that data is not normal and vice versa, but for graphical method what if the data is near to normal distribnution, that when we can cofidently say that our data is normal or not. just like a fix threshold value of p in analytical method.