# How to combine two scale (6 items likert scale and 7 items likert scale) into one index?

#### oscarwukaka

##### Member
Hi, Everyone ! as I mentioned in the topic, may I know how can I actually combine a 6-items-likert scale and a 7-items likert scale) into one index? As you may see in the picture below. I am working on research involving a variable of social identity. And I have found that two scales, group identification scale and group value scale, which are pretty useful, but may I know if it is possible for me to combine a 6-items-likert scale and 7-items likert scale in a formal research. I heard that people can always reduce a 7-items likert scale to a 5 items scale , but how about 7 items to 6 items? The thing is the group identification scale has a neutral value: 4 whereas the group value scale doesn't have it. May I know what is the best way for me to transform the data? should I increase the items of group value scale from 6 to 7 to make an index, or should I decrease the items of group identification scale from 7 to 6?

#### Karabiner

##### TS Contributor
Why do you feel the need to collapse scales which measure distinct concepts into one scale,
what will you do further with the resulting instrument then? Is it not possible to answer your
research question/s by retaining the two variables?

With kind regards

Karabiner

#### oscarwukaka

##### Member
Why do you feel the need to collapse scales which measure distinct concepts into one scale,
what will you do further with the resulting instrument then? Is it not possible to answer your
research question/s by retaining the two variables?

With kind regards

Karabiner
Oh, just an example, what is the best way to do in this situation? should I increase the items of group value scale from 6 to 7 to make an index, or should I decrease the items of group identification scale from 7 to 6?

#### Karabiner

##### TS Contributor
You do want to combine two Likert scales. Therefore it doesn't seem necessary to
change any item response scale, but to consider the whole scales. You could for
example multiply the sum score of the 6-point-scale by 7/6 before adding them up.

Or, you could leave it as it is and use statistical analyses for multiple dependent
variables (multivariate analyses).

With kind regards

Karabiner

#### oscarwukaka

##### Member
You do want to combine two Likert scales. Therefore it doesn't seem necessary to
change any item response scale, but to consider the whole scales. You could for
example multiply the sum score of the 6-point-scale by 7/6 before adding them up.

Or, you could leave it as it is and use statistical analyses for multiple dependent
variables (multivariate analyses).

With kind regards

Karabiner
Thanks ! yep, I will what I can do then. I think changing 6-point-scale value into 7 point is better than changing 7-point-scale into 6 , right ? Also, I want to wish you a great new year ahead, wish you good health and good luck !!

#### Karabiner

##### TS Contributor
I guess you should not change the item response of the single Likert-type items,
but transform the sum score of one of the two Likert scales. In the present example,
you could multiply with 7/6 with one of the sum score, or with 6/7 with the other
sum score.

With kind regards

Karabiner

#### oscarwukaka

##### Member
I guess you should not change the item response of the single Likert-type items,
but transform the sum score of one of the two Likert scales. In the present example,
you could multiply with 7/6 with one of the sum score, or with 6/7 with the other
sum score.

With kind regards

Karabiner
Thanks, you are absolutely right ! Mr. Karabiner, you are the best!!