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Unformatted text preview: ate, !
the MS in Equation 3, is the average of nA numbers from Sample A and nB numbers from Sample B. However, because the formula depends on MA and MB, which are both computed from the data, we “lose” two degrees of freedom. Independent
samples t
test: df = n A + n B " 2 (7) Degrees of freedom in general. Any Mean Square formula is an average of numbers of the 2
ˆ
ˆ
form X " X , where X is some statistic like M. The question is, how many numbers are !
we really averaging? The answer isn’t what it naively seems to be, and this is why we need the concept of degrees of freedom. ! Take the sample variance as an example. Sample variance is the simplest v...
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This document was uploaded on 02/25/2014 for the course PSYC 3101 at Colorado.
 Spring '08
 MARTICHUSKI
 Psychology

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