I'm pretty clueless, but would appreciate any help very much. I have:
Group 1: went from nothing, to receiving surgery 1, and then later on received surgery 2.
-> A (before), B (after first surgery), C (after second surgery)
Group 2: went from nothing to receiving surgery 1
-> A (before), B (after first/only surgery)
These patients have answered questionnaires with several questions and outcomes, at each relevant moment in time (A, B, and C for group 1 only). These outcomes are different, most variables are discrete, one is binomial ("have this affected you positively: yes or no").
Mainly I want to compare outcomes in group 1; was the effect significant after first surgery vs before, or after second surgery vs after first surgery. The data is in most cases not normally distributed.
Question 1: for comparison in between the same group, since the data is not normally distributed, when comparing for example outcome X in time A vs time B, is it correct to use the Wilcoxon one sample test?
Question 2: if one outcome is normally distributed, and one outcome is not (for example outcome x in time A is normally distributed but outcome x in time B is not), do I still use the Wilcoxon one sample test?
Question 3: When comparing the two groups, for example outcome y at time A in group 1 vs the same in group 2, is it correct to use the Wilcoxon rank sum test (Mann-Whitney)? (if the data is not normally distributed)?
Question 4: When comparing the binomial outcome within groups and in between group 1 and group 2, is it the Chi^2 test in both cases, or in neither?
Question 5: Which is the most reliable/easiest method to evaluate whether the data is normally distributed in STATA?
Group 1: went from nothing, to receiving surgery 1, and then later on received surgery 2.
-> A (before), B (after first surgery), C (after second surgery)
Group 2: went from nothing to receiving surgery 1
-> A (before), B (after first/only surgery)
These patients have answered questionnaires with several questions and outcomes, at each relevant moment in time (A, B, and C for group 1 only). These outcomes are different, most variables are discrete, one is binomial ("have this affected you positively: yes or no").
Mainly I want to compare outcomes in group 1; was the effect significant after first surgery vs before, or after second surgery vs after first surgery. The data is in most cases not normally distributed.
Question 1: for comparison in between the same group, since the data is not normally distributed, when comparing for example outcome X in time A vs time B, is it correct to use the Wilcoxon one sample test?
Question 2: if one outcome is normally distributed, and one outcome is not (for example outcome x in time A is normally distributed but outcome x in time B is not), do I still use the Wilcoxon one sample test?
Question 3: When comparing the two groups, for example outcome y at time A in group 1 vs the same in group 2, is it correct to use the Wilcoxon rank sum test (Mann-Whitney)? (if the data is not normally distributed)?
Question 4: When comparing the binomial outcome within groups and in between group 1 and group 2, is it the Chi^2 test in both cases, or in neither?
Question 5: Which is the most reliable/easiest method to evaluate whether the data is normally distributed in STATA?