Question

The effectiveness of a blood-pressure drug is being investigated. An experimenter finds that, on average, the reduction in systolic blood pressure is 41.1 for a sample of size 630 and standard deviation 5.7.

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).

________< μ <____________

Answer should be obtained without any preliminary rounding.

Answer 1

Since n = 630 which is too large, we make use of Z tables.
In general, (1-)% confidence interval for population mean is obtained as follows :

where   = 41.1 ,   = 5.7 and
Z (/2) = Z(0.05) = 1.96

Thus, 90% confidence interval for population mean is :

40.65489687  < μ < 41.54510313
40.7  < μ < 41.5

Hope this answers your query!