Dear Jamovi community,

i am using Jamovi version 1.8.1.0., and i am excited to see that in the Reliability Analysis menu there is an option to SAVE sum scores and mean scores. I tried it out immeadiately, i have four items i analysed with PCA and they combine into a single component, and there are no reversed items. So i supposed that the sum score i can get from the menu (from Reliability analysis) should give me the exact same values i would obtain by simply adding the four values.

However, this is not the case, and i don't understand why.

Moreover, the sum score that I computed and the sum score that resulted from this menu does not even show correlation (only a very week one), while it shows a very high correlation with the PCA component score that i also saved. The reason i am writing this is that if i am right and there is a problem with the sum scores, the problem might extend to PCA component scores as well.

I am also curius how does the program compute sum scores when there are reversed items. Usually, when i compute it for myself, i use a very simple formula to reverse items:

the possible MINIMUM score on the scale + the possible MAXIMUM score on an scale - the ACTUAL score that was given.

However, in the reliability analysis window i can not provide these information, how does it know how to reverse scores?

or i am misunderstanding the aim of these scores, and they show something else?

Thank you!

Emese