Sample size help!!!!


Dear all, so I am really needing help. My dissertation is complete but has a flaw. My supervisor told me to collect 200 questionnaires as part of my triangulation methods and justify this as being representative of 0.138 of the case study population. Now I am told i need to justify this further. I am useless at calculations and need to tailor this to cochrans formula for the 200 questionnaires of which 192 are usable. I need help calculating this or help finding another avenue of justifying this. I used  the chi squared test in the analysis of these 192 usable questionnaires if this helps. PLEASE HELP ASAP.


Can anyone help Shorty?


Hi have you tried using a program called Gpower? It's available free online. You can do sample and effect sizes as either pre or post test.