What tests should I use to analyze my data? Immediate input appreciated

#1
Hello TalkStats members :wave:

I have some data I need to analyze. I first would like to say I hope I am posting this in the correct sub-forum, and I greatly appreciate any suggestions given.

I have 116 "Case" patients, and 100 "Control" patients. Let's say, the "cases" have heart disease and the "controls" do not. Other than the fact that control and cases are separated by heart disease, they were all selected from the same group of patients at a hospital, at random, so they should have similar demographics.

I want to see if these two groups have statistically significant differences in a number of parameters (age, percentage male/female, smoking - which will be a 1 for yes and 0 for no, lung function - which will be a continuous number from 0 to 150% of expected value). I was told by a statistician who only was able to give me 10 minutes of her time that I should use a Wilcoxon test for the continuous variables and a chi squared test for something else.

I am immediately running into the problem of the Wilcoxon needing equal sample sizes. Maybe wilcoxon is not appropriate for me. Does anyone have any suggestions for determining if two groups of equal size have similar or different age/sex/etc.?

Secondly, I would like to combine the two groups into one, with cases being 1's in a column for heart disease and control's being a 0. I would like to know if heart disease, gender, age, smoking (1 or 0), or anything else is linked to difference in the lung status parameter. (perhaps this is a test of correlation, or a test of covariance?)

In case this information is necessary, I am a graduate student doing this for a class. I have a 5pm Monday deadline, so I would greatly appreciate any information you may be able to give me to point me in the right direction. I have JMP software on my computer and access to SPSS and SAS, though I have been told there is no way I will be able to understand SAS.

Thank you in advance for your help
 

Dason

Ambassador to the humans
#2
It can be confusing because there is a Wilcoxon rank-sum test and a Wilcoxon signed-rank test. One is a paired test where you need equal sample sizes because you assume there is dependence between pairs of observations. That's not your case. What I'm guessing is that you want the rank-sum test (also known as the Mann-Whitney test).
 
#3
It can be confusing because there is a Wilcoxon rank-sum test and a Wilcoxon signed-rank test. One is a paired test where you need equal sample sizes because you assume there is dependence between pairs of observations. That's not your case. What I'm guessing is that you want the rank-sum test (also known as the Mann-Whitney test).
Thanks for your help. I am attempting to perform the Mann-Whitney test to complete these calculations. Unfortunately, SPSS is stating that I cannot compare the gender makeup of my sample (by 1 if male, 0 if female) using Mann-Whitney because the "0 or 1" system makes this a nominal category. Would I use another test to determine whether the two groups (Case and Control) had different percentages of men/women, and other nominal data (i.e. smokers/non-smokers)?

[EDIT: the answer to this is probably to use a chi-squared test to see if %males, %smokers is similar in case and control group. Confirmation would be appreciated]
 
Last edited: