I cheat. Well, I use “cheat” sheets. I’ve had plenty of statistics training, but honestly, my brain just doesn’t want to hold onto the assumptions associated with this or that test. So I create little charts or tables, which I reference often. This frees up brain space to continually reassess the pros and cons of buying a used Jeep Wrangler versus a Subaru WRX (three years strong and I still haven’t decided).
Anyway…here’s a quick reference guide for choosing a statistical test:
Answer the following questions:
 What is my variable type?
 Is the comparison group data paired or unpaired? (i.e., can you link data from individual respondents in the two comparison groups or not)
 What is the sample size?
Once you’ve answered these questions, use the following to identify which statistical test of significance to use:
Variable type 
Paired data 
Sample size (in each group) 
Test of significance 
Categorical 
No 
>5 
Chisquare 
<5 
Fisher’s exact test 

Yes 
N/A 
NcNemar’s Test 

Continuous 
No 
>30 
Independent samples ttest 
<30 
MannWhitney U test 

Yes 
>30 
Paired ttest 

<30 
Wilcoxon signedrank test 

Ordinal 
No 
N/A 
MannWhitney U test 
Yes 
N/A 
Wilcoxon signedrank test 