# Re: power calculation

*From*: "Thom" <t.s.baguley@xxxxxxxxxxx>*Date*: 23 Jan 2006 08:00:17 -0800

To do it properly you'll also need more context. Where are the mean

difference, sd and sem of the groups from? Most likely they are from a

pilot study or from previous research and using them as estimates of

the mean difference and sd for a future study. If the future study

differs in design or if the pilot/earlier study have small N that'll

influence the estimate (although in some cases you won't know in

advance how the estimate will change in other cases you can make an

educated guess).

Thom

.

**References**:**power calculation***From:*seren82

**Re: power calculation***From:*Marc Schwartz

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