I have the following 2 samples data 1 : 59.09 59.17 59.27 59.13 59.10 59.14 59.54 59.

Question

I have the following 2 samples data 1 : 59.09 59.17 59.27 59.13 59.10 59.14 59.54 59.

Flakqfqbq 2022-05-08 Answered

I have the following 2 samples
data 1 : 59.09 59.17 59.27 59.13 59.10 59.14 59.54 59.90
data 2: 59.06 59.40 59.00 59.12 59.01 59.25 59.23 59.564
And I need to check whether there is differentiation regarding the mean and the variance between the 2 data samples at significance level a=0.05
I think that the first thing I need to do is to check whether the samples come from a normal distribution in order to infer whether i should proceed using parametric or non marametric tests...
However using lillietest in matlab returned that both samples do not follow the normal distribution...
Any ideas on how should I proceed with checking the differentiation tests ? Should I perform ttest ? Or should I proceed by using something like Wilcoxon ? (p.s please confirm that that both data samples do not follow normal distribution...)

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Answers (1)

Raiden Williamson

Answered 2022-05-09 Author has 15 answers

For a t-test, you need the samples to follow a normal distribution, so you're right to check this assumption first. I did a Shapiro-Wilk to test the normality, and it is rejected for the first sample, but it is not for the second sample. Thus you can't use a t-test.
The alternative is to use the Wilcoxon test, which is non-parametric.
Here is the code I have used with R :
data1 <- c(59.09, 59.17, 59.27, 59.13, 59.1, 59.14, 59.54, 59.9)
data2 <- c(59.06, 59.4, 59, 59.12, 59.01, 59.25, 59.23, 59.564)
shapiro.test(data1)
# P-value = 0.007987. Normality is rejected.
shapiro.test(data2)
# P-value = 0.3873. Normality is not rejected.
wilcox.test(data1, data2)
# P-value = 0.5054. No significative difference.