Regression analysis, Reliability and Validity.

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Regression analysis, Reliability and Validity.

Postby colene » Sat Apr 05, 2014 12:28 am

Hi there - working on my assignment for an introduction course in kvantative method in uni. (English is not my first language, so pardon anything oddly explained.)

It's a group assignment where we have completed questioneer with 10 questions, done the field work and now we have the data which we have to analyse in relation to our question. Where we want to see if there is a 'connection' between student work hours and whether or not they rent a doorm room or rent privatly.

I have problems understanding various calculatings in SPSS and how to execute it - hopefully someone can drop by now and then and answer my questions here.
Does anyone know of an SPSS chatroom somewhere?

My part of the group work is doing the regression analysis and elaborating on the reliability and validity of our work.

I would like to run a Cronbachs alfa test (or similar if you have an alteriour suggestion) to include it in my reliability part.

I have a mixture of variables - Nominal, Ordinal and scale.
Which have a whole range of diferent ranges in values. Some variables have 0-1, others have 1-5, while others go from 0-14000. None are similiarly kategorized. Like, sex is a 0-1. Work hours range pr week from 0-30. A satisfactory question ranges from 1-5, rent payed ranges from 500- 13000... etc..

I've kategorized rent, and when I lump them all togheter in SPSS - Cronbachs alfa I get a Cronbachs Alfa of around ,500.
BUT - I have a feeling this is quite pointless? Because of the state of the values - is this so, is Cronbachs Alfa usless - how would I explain that I can't use Cronbachs Alfa? My corriculum states that it is restricted to indexes - But I can't quite understand what this means by "indexes". Certainly we have an index of questions that all aim to answer a question - but it's not an index where all numbers are grouped simillarilly - so i am unsure what it means...
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Re: Regression analysis, Reliability and Validity.

Postby GerineL » Mon Apr 07, 2014 8:13 am

you can use cronbach's alpha in cases you have multiple questions assessing the same question.
For instance, a satisfaction with living situation scale consisting of 6 items.
It is based on internal consistancy, more or less: The tendency to respond similarly on different items measuring the same thing.

Seen as the constructs you mention do not measure the same thing, you cannot use cronbach's alpha.
in addition, you cannot use it like this with different scales. There are some people that would argue you can transform all scales to z-scores first and then calculate cronbach's alpha. But this will only work with scales (i.e., not with nominal data).

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