# Recent content by Sobath

1. ### What test should be used to compare nominal data between 5 groups

Dear yl2010fall, many thanks for your response. Is Cochran Armitage Trend test is appropriate only when one variable has two levels and the other variable is ordinal. I can take the years as the ordinal variable but still will it work in my case? I wanted to find out if there is a up or...

3. ### What test should be used to compare nominal data between 5 groups

can I use Cochran–Mantel–Haenszel Test to compare the frequencies between different years?
4. ### What test should be used to compare nominal data between 5 groups

Dear All, I am a surgeon trying to investigate how indications for a device has changed over 5 years. I have the following data set for patients; I want to find out for each indication if there is a trend or a statistically significant relationship over the years. What is the best statistical...
5. ### Sample size calculation

We are not looking at AT. We want to look at the aortic diameter change. Therefore outcome measures will be numerical data. Change in aortic diameter in millimetres.
6. ### Sample size calculation

If I use a control group, should I use ANOVA to compare cases and controls?
7. ### Sample size calculation

Dear hlsmith, thanks for the message. Yes, we are including a control group.

9. ### Sample size calculation

We want to look at both. (1) Is there a pre/post difference? (2) If so wat what levels in the aorta. These findings will translate into sizing a stent to stem life-threatening bleeding. There are common places where we see more bleeding and hence the need to look at different points in the aorta.
10. ### Sample size calculation

Many thanks for the above. Is ANOVA better than the paired t-test for this particular situation, as it is not known if the data is parametric?
11. ### Sample size calculation

Dear Miner, Many thanks. Yes location is important. We are looking at how different points in the human aorta behave in critically injured (road traffic accident etc.) patients on arrival and after fluid therapy. There’s data from the small study (n=43) I mentioned, that there is a significant...
12. ### Sample size calculation

Dear Minder, Many thanks for your response. I will definitely use your advice. Thanks. If I want to compare more points in the aorta (5 points ), do I need to increase the sample size?
13. ### Sample size calculation

Dear All, I am a vascular surgeon planning a research project. I need some advice regarding the sample size calculation. I am looking at the same group of patients pre and post-procedure looking for a change in the diameter of their main blood vessel at 2 different points. We have some data...