Combining multiple std.devs or combining different datas

jahahus

Hi there!

I've created a questionnaire with three "categories" (Cx) and four sub questions (Qy) for each category:

C1:

C1Q1... (1-7)

C1Q2... (1-7)

C1Q3... (1-7)

C1Q4... (1-7)

C2:

C2Q1... (1-7)

C2Q2... (1-7)

C2Q3... (1-7)

C2Q4... (1-7)

All questions are answered by 10 respondants.

I've managed to find the std.dev for each question in SAS JMP:

Column 1:

1: 3

2: 3

3: 4

4: 5

5: 5

6: 6

7: 6

8: 7

9: 7

10: 7

My question is: How should I find the std.dev for the whole category?

Put all 4*10 answers in column 1?

brady_brady

One easy way to do this is to put the data into 4 columns: Category #, Question #, Respondent# and Score. (See table below.)

Then create 2 new columns and add the formulas shown below.

For the standard deviation of the category:

For the standard deviation of the question (within category):

Starting with the same table, you could alternatively use Table->Summary, finding the stddev of Score, grouping once by category, and again by category and question.

Cheers,

Brady