Good day,

Ive been doing a research about asking people to answer a set of questions twice with 2 wks apart. my statistician uses phi coefficient for the test retest reliability and the result range from 0 to 1. my question is what range can we say the result is poor, good or very good?

Another questions is about kuder richardson 20 which my stat use also..i also have the same question like is there a range that we can say its a poor, good or excellent result?

If you guys have the answer, maybe you can also site the book as reference for my paper?