[Rasch] development and validation of instrument

Juanito Talili talilij at yahoo.com
Fri Jun 13 10:38:42 EST 2008

We develop a 50-item instrument anchored on a theory with 4 constructs. We piloted the instrument to 203 persons, then we subjected to Rasch analysis.  After our Rasch analysis we found that the 50 items are unidimentional and the 5-point likert scale categories are logically functional, but while retaining the 4 constructs, five items misfit the model.  Thus, we decided to remove the 4 items and come up with a 45 item instrument.  Our questions to Rasch expert are:
1. Shall we gather again another data(say n=200) to validate the instrument?
2. How do Rasch validation is done? Do we just repeat the rasch analysis?
3. Is our sample enough for Rasch analysis?
Thank you.

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