Stata command for comparing count/frequency data between two time periods?

[Insung Kang]

Hello Statalist,

I'd like to ask which statistical model I need to use to compare frequency data (e.g., never, rarely, sometimes, frequently, always) and count/incidence data (yes, no) between two time periods within the same groups (not between group), and to get p-value?

Thank you for your help in advance!

[Joseph Coveney]

Your description of the variables in your dataset doesn't make sense to me for either a within-group or between-group data structure.

For a within-group structure at each of two times with single groupwise count variable (in lieu of an individual member ID variable), I would have expected something like what you get after running the following lines.

version 17.0

clear *

// seedem
set seed 823830557

quietly set obs 5
generate byte rarity_score1 = _n - 1

quietly expand 5
bysort rarity_score1: generate byte rarity_score2 = _n - 1

label define RarityScores 0 Never 1 Rarely 2 Sometimes 3 Frequently 4 Always
label values rarity_score? RarityScores

generate int count = runiformint(50, 500)

label variable rarity_score1 "Frequency data, Period 1"
label variable rarity_score2 "Frequency data, Period 2"
label variable count "Count/incidence data"

list, noobs abbreviate(20) sepby(rarity_score1)

exit

Does your dataset look like that?

Note that the "count/incidence data" variable is not Boolean, not a "(yes, no)" type.

[Insung Kang]

Thank you Jeseph!

I added an example of the dataex. I'd like to compare hospital visit (hospital1 vs hospital2) and frequency (frequency1 vs frequency2). In this case, which statistical model I can use to get p-value?

* Example generated by -dataex-. To install: ssc install dataex
clear
input float personid str3 hospital1 str10 frequency1 str4 hospital2 str10 frequency2
 1 "yes" "always"     "yes" "always"    
 2 "yes" "sometimes"  "yes" "always"    
 3 "yes" "never"      "yes" "sometimes" 
 4 "no"  "always"     "yes" "sometimes" 
 5 "no"  "rarely"     "yes" "rarely"    
 6 "no"  "frequently" "no"  "frequently"
 7 "no"  "sometimes"  "no"  "always"    
 8 "no"  "always"     "no"  "always"    
 9 "no"  "always"     "no"  "always"    
10 "no"  "never"      "no"  "sometimes" 
end