Confidence Intervals (Mean)

Question

The effectiveness of a blood-pressure drug is being investigated. An experimenter finds that, on average, the reduction in systolic blood pressure is 54.5 for a sample of size 29 and standard deviation 15.4. Estimate how much the drug will lower a typical patient's systolic blood pressure (using a 80% confidence level). Assume the data is from a normally distributed population.  

Enter your answer as a tri-linear inequality accurate to three decimal places.

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Answer 1

CI = mean +/- z-critical for 80% CI * standard deviation/square root (sample size)

z-critical for 80% CI is 1.28.

mean, standard deviation and sample size are given in problem.