How to Calculate the pvalue

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How to Calculate the p-value
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There Are 2 Possibilities

• Left or Right Tailed Test (case 1)
• Two Tailed Test (case 2)

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Case 1 Left or Right Tailed Test
If the claim involves an inequality (either lt or
gt) then the test is a one tailed test. This means
that the p-value will be in one tail or the other
but not both. Lets look at a left tailed
example Claim The mean score on the verbal
portion of the GRE is at least 500. This means
the claim is So, the alternate will be given
by
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Case 1 Left or Right Tailed Test
If we are given that the test resulted in a z
-2.67 then we are being asked to find the
probability of seeing that value or more extreme
in the distribution of the null hypothesis. Since
it is a left tailed test that is from -E99 to
-2.67. I have exaggerated the drawn area to help
see it. The calculation is done using
normalcdf(-E99,-2.67,0,1) 0.004 Note the
procedure is the same for a Right Tail.
0.004 probability
-2.67 z
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Case 2 Two Tailed Test
If the claim involves an equality () then the
test is a two tailed test. This means that the
p-value will be in one tail and the other. Lets
look at a two tailed example Claim The mean
score on the verbal portion of the GRE is 500.
This means the claim is So, the alternate
will be given by
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Case 2 Two Tailed Test
If we are given that the test resulted in a z
-2.67 then we are being asked to find the
probability of seeing that value or more extreme
in the distribution of the null hypothesis. Since
it is a two tailed test that is from -E99 to
-2.67 and from 2.67 to E99. Again I have
exaggerated the drawn area to help see it. The
calculation is done using 2normalcdf(-E99,-12.67
,0,1) 0.008.
0.008 probability
-2.67 z
2.67 z