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Combining multiple std.devs or combining different datas

jahahus

Community Trekker

Joined:

Apr 2, 2014

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?

1 ACCEPTED SOLUTION

Accepted Solutions
Solution

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.

5893_pastedImage_0.png

For the standard deviation of the category:

5894_pastedImage_1.png

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

5895_pastedImage_2.png

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

4 REPLIES
Solution

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.

5893_pastedImage_0.png

For the standard deviation of the category:

5894_pastedImage_1.png

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

5895_pastedImage_2.png

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

jahahus

Community Trekker

Joined:

Apr 2, 2014

Hey Brady!

Thanks for a great answer!

Could you please explain what the numbers in two extra columns indicates? Why "1.501192665"?

Thanks.

brady_brady

Staff

Joined:

Jun 9, 2012

The standard deviation of all responses in category 1 was that value. (In your example, there would be 10*7 = 70 responses in category 1... so the first 70 rows of the data table are all going to have this same value in the "Cat Stddev" column. If you used the summary platform instead of the formula approach, you'd get the following table:

5898_pastedImage_0.png

Cheers,

Brady

jahahus

Community Trekker

Joined:

Apr 2, 2014

Thanks again!

I think I've got a bit different version (JMP 10), but I put Score in Y and sorted by "category, question" and then only "category". I think I got it!

Thanks for the help.