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where :, is the standard normal value associated with the smallest significance level at which the null hypothesis can be rejected. The p-value is regularly com- puted by most statistical computer programs based on the computed single sample mean and provides more information about the test, based on the ob- served sample mean. Thus, it is a popular tool for many statistical applications. 92 Test of the Mean of a Normal Dutribution Palation Variance Known 335 u52 It is important to note that the p-value is an observed random Variable that will be dif- ferent for each random sample obtained for a statistical test. Thus, two different analysis could obtain their own random samples and sample means from a process population. and, thus, each would compute a different p-value Example 9.1 Evaluating a New Production Process (Hypothesis Test) The production manager of Northern Windows. Inc. has asked you to evaluate a pro- posed new procedure for producing its Regal line of double-hung windows. The pres- ent process has a mean production of 80 units per hour with a population standard deviation of r = & The manager does not want to change to a new procedure unless there is strong evidence that the mean production level is higher with the new process