SOLUTION: The effectiveness of a blood-pressure drug is being investigated. An experimenter finds that, on average, the reduction in systolic blood pressure is 62.6 for a sample of size 820

Question 1187309: The effectiveness of a blood-pressure drug is being investigated. An experimenter finds that, on average, the reduction in systolic blood pressure is 62.6 for a sample of size 820 and standard deviation 13.6.
Estimate how much the drug will lower a typical patient's systolic blood pressure (using a 90% confidence level).
Enter your answer as a tri-linear inequality accurate to one decimal place (because the sample statistics are reported accurate to one decimal place).
Answer by Boreal(15235) (Show Source): You can put this solution on YOUR website!
90% half-interval is a t(0.95, df=819)=1.645* s/sqrt(n). This is essentially z, but when there is a sample with a sample sd, t should be considered, and then with a large sample size use z.
interval is 1.645*13.6/sqrt(820)=0.78
the 90%CI is (61.82, 62.38) mm Hg
or (61.8 < mu < 62.4) mm Hg

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