The range of scores within which the population mean is
likely to fall.
The exact width of the confidence interval is determined with
a statistic known as Student’s t
If we set alpha = .05,
Example. Now, we sampled 100 students.
Degree of freedom = 100 - 1 = 99
The appropriate t value = 1.99 (see Table C, Appendix E)
Lower limit _ = - t(s ) = 3.40 - 1.99 ( .22) = 2.96
Upper limit _ = - t(s ) = 3.40 +1.99 ( .22) = 3.84
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