Normality assumptions in SPSS


I have a few questions regarding tests for normality in SPSS.

1. 2 out of 12 values didn't meet normality assumptions (refer to the picture) it means I have to look at the sample size and it's 16 for either group. As a rule, sample size has to be larger than 30 if normality is failed to run a parametric test. Do both groups have to be >30 separately or a combined total of >30 is enough to assume normality?
normality spss.png

2. Similar question but this time about correlation. Normality (Shapiro-Wilk) was failed but this time I don't divide into two groups and my sample size is 32 which is >30. Is it enough to run Pearson's correlation or should I switch to Spearman's?


Well-Known Member
When the sample size is big (some say >30) you may assume normality even if the source is not normal, per central limit theorem

with a small sample, usually, the normality test will not have enough power to prove non-normality.
In your case, I assume you should run a parametric test since you proved the non-normality.

ps did you draw histogram?