Negative combach's alfa in evidence based questionnaire

GentlemanA

New Member
Hey everyone,

For a small research I had to do I used the Rosenberg Self-esteem scale and tried to look for correlations with aggression using the Buss Perry Aggression Scale.

Even though it proved very much insignificant I also found a negative crombach's alfa linked to the rosenberg scale.
I checked the coding which was correct. Does anyone have any idea what I'm doing wrong?

You can find the syntax and dataset in this file.

Cheers,

Gent.a

spunky

Can't make spagetti
do you know...

(b) average inter-item correlation?

GentlemanA

New Member
Small research:

N=30

Item-Total Statistics
Scale Mean if Item Deleted Scale Variance if Item Deleted Corrected Item-Total Correlation Cronbach's Alpha if Item Deleted
a. The value is negative due to a negative average covariance among items. This violates reliability model assumptions. You may want to check item codings.

Inter-Item Correlation Matrix
RSS1R 1,000 -,276 ,219 -,213 ,389 -,135 ,476 ,176 ,420 -,068
RSS2R -,276 1,000 ,078 -,053 -,283 ,147 -,445 -,641 -,131 ,552
RSS4R ,219 ,078 1,000 -,196 ,128 -,312 ,024 -,002 ,278 ,003
RSS6R -,213 -,053 -,196 1,000 ,043 ,229 -,121 ,160 -,155 -,254
RSS7R ,389 -,283 ,128 ,043 1,000 -,582 ,524 ,398 ,518 -,712
RSS3R2 -,135 ,147 -,312 ,229 -,582 1,000 -,226 -,398 -,139 ,201
RSS5R2 ,476 -,445 ,024 -,121 ,524 -,226 1,000 ,380 ,420 -,543
RSS8R2 ,176 -,641 -,002 ,160 ,398 -,398 ,380 1,000 ,286 -,456
RSS9R2 ,420 -,131 ,278 -,155 ,518 -,139 ,420 ,286 1,000 -,504
RSS10R2 -,068 ,552 ,003 -,254 -,712 ,201 -,543 -,456 -,504 1,000

GentlemanA

New Member
Reliability Statistics
Cronbach's Alphaa Cronbach's Alpha Based on Standardized Itemsa N of Items
-,241 -,209 10
a. The value is negative due to a negative average covariance among items. This violates reliability model assumptions. You may want to check item codings.

spunky

Can't make spagetti
would you be so kind as to clean up the SPSS data file that you uploaded and ONLY leave the variables that you're using to calculate alpha?

i'd like to try a couple of things on your data.

(ps- it's so awesome to have graduated. now i have all the time in the world to do whatever i want, heh....)

GentlemanA

New Member
Heu,
Yesterday the library closed so this is a bit late but I'll clean up the data after work and post it here.
Thank you for considering to help

Lazar

Phineas Packard
Half the Rosenberg scale is negatively worded. You need to reverse code those items. Not that it is relatively common that this scale factors out to two scales one consisting of the positively worded items and one the negatively worded items. Some people call the two factors self-esteem and depression.

spunky

Can't make spagetti
Half the Rosenberg scale is negatively worded.
i didn't know that, but it makes a lot of sense. when i was looking at the datat the OP posted there seemd to be a chunk of negatively-correlated items on one part of the correlation matrix and a chunk of positively-correlated items on the other.

so i'm guessing it's a re-group and re-code kinda deal now...

noetsi

No cake for spunky
In SEM they always stress the dangers of some questions being coded negatively and others positively. I never understood why that mattered until now.

Will this effect factor analysis and or regression as well? We never checked in our surveys if questions were positively or negatively worded.