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Unformatted text preview: ttest 6/9/11 Lecture 21 1 Last class: tdistribution: helps us do statistical inference when population SD is unknown Computed confidence intervals Today: Testing hypothesis using tdistribution 6/9/11 Lecture 21 2 For CI and hypothesis testing about a normal mean , when is unknown , the sample standard deviation s is used to estimate . Note: replaced by When is the mean of a random sample of size n from a normal distribution with mean , then has a t distribution with n  1 degrees of freedom (df). X n s X t / n X z / t 6/9/11 Lecture 21 3 To determine number of workers required to meet demand, the productivity of new trainees is studied. It is believed trainees can process more than 450 packages per hour within one week of hiring. A sample of productivity of 50 trainees is observed and summarized as: Can we conclude that this belief is correct based on the sample? . 83 . 38 , 38 . 460 s x 6/9/11 Lecture 21 4 Null hypothesis: H : = Test statistic: H a pvalue 2P (T t ) > P (T t ) < P (T t ) ....
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 Summer '08
 AndrewB.Nobel

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