P-Value for upper-tailed t-test, df = 19, t = -0.4

MarkSA

Junior Member
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Sep 8, 2007
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243
Hello,

I'm having some trouble with this question. I thought I was doing this correctly but the answers from the back of my book say it is a different answer. It's been wrong before so I thought I would ask.

Q: Give the p-value of the t test in the following situation:
b) Upper-tailed test, df = 19, t = -0.4

What I did was just to look up the t-curve tails in the table in my book. The table only contains positive values of t. If I look up a degrees of freedom v=19 and t=0.4, the book gives a value of 0.347. But I thought I should be doing 1-0.347 to get the correct value since t is negative. This would give me a p-value of 0.653. But that's not what the answer key has - it says the answer is 0.347. Which should be correct?
 
I think the answer key is wrong. Your calculation is equivalent to \(\displaystyle P(T > -.4|df=19)\), which is the proper P-value for an upper tail test.
 
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