If you have 4 Likert items, for example y1, y2, y3 and y4. Then a usual way it to just sum them, like:
Index1 = y1 +y2+ y3 + y4.
Or you can,if you prefer that, you can give different weights to different items (like giving higher weight w1 to y1 if you think that y1 is more important than the rest).
Index2 = w1*y1 +w2*y2+ w3*y3 + w4*y4,
where w1+w2+w3+w4 = 1 (so that the weights sum to 1, just like the weighted mean.)
Now you can use Index1 or Index2 to calculate a correlation coefficient towards an other variable.
Index1 = y1 +y2+ y3 + y4.
Or you can,if you prefer that, you can give different weights to different items (like giving higher weight w1 to y1 if you think that y1 is more important than the rest).
Index2 = w1*y1 +w2*y2+ w3*y3 + w4*y4,
where w1+w2+w3+w4 = 1 (so that the weights sum to 1, just like the weighted mean.)
Now you can use Index1 or Index2 to calculate a correlation coefficient towards an other variable.
Excel?!! Oh, horror! Please, don't do it in excel!!
You point and click and after three months you don't remember anything of what you did. Your work should be reproducible.
Maybe you can use excel to enter the data (and control read it with a friend. (All of us makes mistakes. You too!))
Then read in the data to spss. Don't click on the "OK" button, click on the "Paste" button. That will give you a syntax file ( an *.sps file). There all your commands will be added. You save that file and re-use it next time you want to change or add something. Now, your work will be "reproducible", which is a good thing. And you will also have documentation of what you did. Write many comments, like:
* this is my index formula blah blah.
(A comment starts with a "*" and ends with a period ".".)
You point and click and after three months you don't remember anything of what you did. Your work should be reproducible.
Maybe you can use excel to enter the data (and control read it with a friend. (All of us makes mistakes. You too!))
Then read in the data to spss. Don't click on the "OK" button, click on the "Paste" button. That will give you a syntax file ( an *.sps file). There all your commands will be added. You save that file and re-use it next time you want to change or add something. Now, your work will be "reproducible", which is a good thing. And you will also have documentation of what you did. Write many comments, like:
* this is my index formula blah blah.
(A comment starts with a "*" and ends with a period ".".)