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?