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A standardized test is given to a sixth grade class.Historically the mean score has been 156 with a standard deviation of 17.
A standardized test is given to a sixth grade class. Historically the mean score has been 156 with a standard deviation of 17. The superintendent believes that the standard deviation of performance may have recently decreased. She randomly sampled 26 students and found a mean of 146 with a standard deviation of 15.2474. Is there evidence that the standard deviation has decreased at the α=0.05 level?
Step 1 of 5 : State the null and alternative hypotheses. Round to four decimal places when necessary.
Step 2 of 5 : Determine the critical value(s) of the test statistic. If the test is two-tailed, separate the values with a comma. Round your answer to three decimal places.
Step 3 of 5: Determine the value of the test statistic. Round your answer to three decimal places.
Step 4 of 5: Make the decision.
Step 5 of 5: What is the conclusion?
