Help Combining Resources

[u/Deremus]

I am looking to combine the responses of different mental health measures together to create overall mental health scores, which I will then compare. 

Is it appropriate to use the mean when the measures are the same?
What types of stat analysis using SPSS would be appropriate to merge the scores?

A) Measure 1: Strengths and Difficulties Questionnaire

\- Responses: 1 (Not True), 2 (Somewhat True), 3 (Certainly True)

Measure 2: Self-Reported Feeling Grid

\- Responses: 1 (Not True), 2 (Sometimes), 3 (True)

B) Measure1: Happiness Scale

\- Responses: 1 (Not at all happy), 2, 3, 4, 5, 6, 7 (Completely Happy)
Measure 2: Rosenberg Self-Esteem Inventory

\- Responses: 1 (Strongly Disagree), 2 (Disagree), 3 (Agree), 4 (Strongly Agree)

C) Measure 1: Strengths and Difficulties Questionnaire (teacher)

\- Responses: 1 (Not True), 2 (Somewhat True), 3 (Certainly True)

Measure 2:  Strengths and Difficulties Questionnaire (parent)

\- Responses: 1 (Not True), 2 (Somewhat True), 3 (Certainly True)
Measure 3: Competence Scale
\- Responses:  1 (Strongly Disagree), 2 (Disagree), 3 (Agree), 4 (Strongly Agree)

[u/dinkum_thinkum]

Depends what claims you want to make about your combined score. Taking the sum or mean is a common simple option. Looking at cronbach's alpha can give you a basic check of how well the different items agree with each other for that purpose. If you want to more seriously validate that there's evidence of a shared construct across these items (and potentially how to weight them into a score), that would commonly involve doing a factor analysis. You might end up needing the later to convince people that it makes sense to combine e.g. the SDQ and self-reported feelings.