“T scores: statistics”?

Published October 23, 2010

Question by Kaitlin F: “T scores: statistics”?
When you are getting the t-score with a degree of freedom of lets say, 38, do you round up and use df of 40 or round down and use df of 30? What if your df was 32? Round up or down? 35? Is there a rule as to when you round up and down?

Thanks!

Best answer:

Answer by h22page
say df=35 and alpha =0.05, the equation to find the t value is….

use the t-table in the back of the book to find the t-value

since, 35 is not listed, look at the 30 and the 40 values of t.

so, for 30, t=2.042
and for 40, t=2.021

now, t-value of lower df – (difference of low df and wanted df)/ by difference of lower df and higher df) times (difference of lower t-value minus higher t-value)

kinda confusing….
df=2.042-(35-30)/(40-30)*
(2.042-2.021)
df=2.042-(5/10)*0.021
so, for a df=35, the t-value=2.0315

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