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How to Use This Table
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This table contains the upper critical values of the
Student's t-distribution. The upper
critical values are computed using the
percent point function.
Due to the symmetry of the t-distribution, this table can be used
for both 1-sided (lower and upper) and 2-sided tests using the
appropriate value of .
The significance level, , is
demonstrated with the graph below which plots a t distribution with 10
degrees of freedom. The most commonly used significance level
is = 0.05. For a two-sided test,
we compute the percent point function
at /2 (0.025). If the
absolute value of the test statistic is greater than the upper
critical value (0.025), then we reject the null hypothesis. Due to
the symmetry of the t-distribution, we only tabulate the
upper critical values in the table below.
Given a specified value for :
- For a two-sided test, find the column corresponding to
/2 and reject the
null hypothesis if the absolute value of the test statistic is
greater than the value of
in
the table below.
- For an upper one-sided test, find the column corresponding to
and reject the null
hypothesis if the test statistic is greater than the tabled
value.
- For an lower one-sided test, find the column corresponding to
and reject the null
hypothesis if the test statistic is less than the negative of
the tabled value.
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