I have an x-ray evaluation of patients. Each patient was seen in the clinic at different time intervals (Days between xrays), not regular times.

There are different rates of application to clinics for patients (at least 3, at most 10 or more times)

X-rays were evaluated for a certain difference, if an observer thinks there is a difference, he ticks "True", or vice versa.

All evaluation will be done by the same observers at 2 weeks interval, at a random fashion done by the software.

I am looking for:

1. How can we calculate the power of this study.

2. The lowest "Days between xrays" agreement between observers for all patients in general (interobserver & intraobserver correlation) (We may set "days" interval such as 100, 150, 200, 250, 300, etc)

3. Is there a difference of "lowest days between xrays" between sex?

4. Is there a difference of "lowest days between xrays" between different age margins? (30 - 50 years, 51 - 60 years, 60 - 70 years, 70 and over years)?

Thank you for your response.