Determining Reliability for Likert Scale Questions Using Chronbach's Alpha in SPSS

[@kossonouprunelle7576]

i have 12 items with 26 questions in my questionnaire (6 likert scale, 3 nominal and 3 ordinal items). Should i measure Cronbach Alpha for the entire scale
? Or choose some between them to check the reliability of my questionnaire? Thank you for the presentation

[@charliepower9609]

You didn't explain WHY they were reliable