New -omega- command

[Brian Shaw]

Happy Monday to all. There is a new module, -omega-, now available on the SSC, that calculates the ω reliability coefficient in a single command. ω is similar but preferable to Cronbach's alpha because Cronbach's alpha has many statistical assumptions that are rarely met in practice. The literature has been encouraging a move toward ω as the primary reliability coefficient and now it's easy to use in Stata. I hope you find it helpful and please let me know if you find a bug.

Cheers,
Brian Shaw

[Yapeng Wang]

Dear Brian, thank you for proving the command. I am using your command -omegacoef- in Stata 16.1 (MP) to calculate the omega coefficient for a scale using 6 variables (see data example below). However, Stata returned the following error message. I was wondering if you could let me know what I need to do to get the correct results. Thank you!

* Example generated by -dataex-. To install: ssc install dataex
clear
input byte(Q158_rvs Q159_rvs Q160 Q161 Q162 Q163_rvs)
 9 7  .  9  3  7
 8 6  .  .  1  5
 1 .  .  1  5  3
 1 3  9  7  7  1
 4 3  7  .  2  3
 2 1 10  1  1  4
 3 1 10  9  2  1
 1 5  8  7  4  4
 1 1 10 10  1  1
 1 1 10  3  1  1
 2 2  7  7  6  4
 3 4  8  5  7  3
 3 5  7  8  6  5
 2 4  5  4  7  5
 3 2  5  4  9  3
 2 1  2  1  5  3
 6 1  8  1  7  6
 8 3  1  1  5  4
 6 5  6  3  7  7
 1 3  5  5  3  4
 4 1  8  8 10  1
 4 3  6  9  9  5
 3 2  7  6  7  7
 4 3  5  5 10  5
 3 4  8  5  6 10
 1 1  9  9  9  5
 1 5  8 10  8  3
 1 1 10  1 10  1
 1 1 10  5  1  4
 1 4  7 10  2  4
 4 4  2  1  1  6
10 7 10  8  5  6
 4 4 10  5  5  4
 7 8  9  9  2  3
 8 2  6  9  5  3
 4 7  8  .  1  4
 5 5  6  6  6  4
 7 5  6  5  6  7
 4 4  4  2  5  7
 8 7  .  . 10  3
 3 3  9  2  1  1
 1 4 10  4  1  1
 1 1 10 10  1  1
 2 1 10  6  4  2
 1 1  1  7  1  1
 1 1 10  3  2  1
 1 1  8  2  2  1
 3 4  9  7  8  3
 3 2  5  4  3  3
 3 2  7  5  3  3
 7 7  5  5  4  3
 3 3  5  6  8  4
 2 2  9  6  3  5
 3 3  7  9  9  3
 2 1  1  1  8  3
 3 1  7  6  7  3
 1 1  7  5  4  .
 . .  .  .  .  .
 6 2  5  1  4  7
 3 1  6  3  6  6
 1 1  8  3  5  4
 1 1  3  1  1  2
 8 2  9  4  5  7
 1 1 10  7  8  4
 3 1  4  5  6  .
 6 6  5  5  5  4
 3 3  3  5  1  9
 3 1  5  7  8  3
 1 6  5  3  5  3
 6 3 10  5  3  3
 5 6  6  5  5  3
 6 6  5  5  5  2
 3 3  5  5  5  3
 5 5  1  1  1  2
 1 1  5  4  4  3
 1 1 10  6 10  1
 2 1  9  8  9  2
 1 1 10  1  1  1
 1 1  3  1  1  4
 1 1 10  1  5  2
 4 4  6  1  5  5
 1 1  5  1  1  3
 2 2  5  1  1  3
 1 1  9  2  3  4
 1 7 10  1  9  3
 1 1  7  9  3  4
 4 1  9 10  9  5
 3 1 10  7  5  5
 1 2  9 10 10  3
 6 3 10 10  5  5
 1 2  9 10  9  3
 2 1 10  2  8  4
 2 1 10  7 10  2
 1 2  9 10  9  3
 1 2 10  9 10  4
 6 6  3  5  5  8
 4 3  7  7  7  6
 4 4  8  7  7  4
 1 1  5  1  1  5
 1 1  5  4  4  6
end
label values Q158_rvs Q158_rvs_L
label def Q158_rvs_L 1 "completely agree", modify
label def Q158_rvs_L 10 "completely disagree", modify
label values Q159_rvs Q159_rvs_L
label def Q159_rvs_L 1 "completely agree", modify
label values Q160 Q160
label def Q160 1 "Completely disagree", modify
label def Q160 2 "2", modify
label def Q160 3 "3", modify
label def Q160 4 "4", modify
label def Q160 5 "5", modify
label def Q160 6 "6", modify
label def Q160 7 "7", modify
label def Q160 8 "8", modify
label def Q160 9 "9", modify
label def Q160 10 "Completely agree", modify
label values Q161 Q161
label def Q161 1 "Completely disagree", modify
label def Q161 2 "2", modify
label def Q161 3 "3", modify
label def Q161 4 "4", modify
label def Q161 5 "5", modify
label def Q161 6 "6", modify
label def Q161 7 "7", modify
label def Q161 8 "8", modify
label def Q161 9 "9", modify
label def Q161 10 "Completely agree", modify
label values Q162 Q162
label def Q162 1 "Completely disagree", modify
label def Q162 2 "2", modify
label def Q162 3 "3", modify
label def Q162 4 "4", modify
label def Q162 5 "5", modify
label def Q162 6 "6", modify
label def Q162 7 "7", modify
label def Q162 8 "8", modify
label def Q162 9 "9", modify
label def Q162 10 "Completely agree", modify
label values Q163_rvs Q163_rvs_L
label def Q163_rvs_L 1 "a lot better off", modify
label def Q163_rvs_L 10 "a lot worse off", modify

[Joseph Coveney]

Try this.

rename *, lower
omegacoef q*

Do-file and SMCL log file attached.

[Yapeng Wang]

Try this.

rename *, lower
omegacoef q*

Do-file and SMCL log file attached.

It works. Thank you so much!

[Brian Shaw]

Dear Yapeng, I came to answer this question but Joseph already did. As of now, -omegacoef- does not support variable names that begin with a capital letter.

Updating the -omegacoef- command to address this has been on my to-do list for some time now. I hope to upload a new version shortly. Happy reliability estimation!

[Yapeng Wang]

Dear Yapeng, I came to answer this question but Joseph already did. As of now, -omegacoef- does not support variable names that begin with a capital letter.

Updating the -omegacoef- command to address this has been on my to-do list for some time now. I hope to upload a new version shortly. Happy reliability estimation!

Dear Brian: Thank you! I l look forward to the new version!

[Chen Samulsion]

Another source of discussion, especially in #5 Dirk Enzmann provide a new command -omega2-, and where Yapeng Wang have got an answer:
https://www.statalist.org/forums/for...mega-and-alpha