to do power analysis to estimate your sample size, you have to write your hypothesis, and based on that you decide what statistical test you will use. It should be one of the inferential statistics. so you need to determine the following: alpha {standard to be .05}, power [standard to be .80], effect size {small, moderate, or large, each test has its own value, you can find these values in the net}. Then download free programs to calculate the sample size such as G. power.

Google How to use Gpower. There are some very useful tutorials on how to use this software.

http://www.ats.ucla.edu/stat/gpower/pairedsample.htm

You can use the power and size calculator in: http://powerandsamplesize.com/Calculators/

to do power analysis to estimate your sample size, you have to write your hypothesis, and based on that you decide what statistical test you will use. It should be one of the inferential statistics. so you need to determine the following: alpha {standard to be .05}, power [standard to be .80], effect size {small, moderate, or large, each test has its own value, you can find these values in the net}. Then download free programs to calculate the sample size such as G. power.

I am presently doing course RES/720. I can not afford SPSS software!! I am experiencing difficulty downloading G* Power. I need urgent help in downloading G* Power! PLEASE HELP? Thanks.

G Power calculates overall sample size of study or it provides individual sample size of every group?

Karen George-Durieux please check this link https://g-power.apponic.com/