Twenty-five blood samples were selected by taking every seventh blood sample from racks holding 187 blood samples from the morning draw at a medical center. The white blood count (WBC) was measured using a Coulter Counter Model S. The mean WBC was 8.636 with a standard deviation of 3.9265.
(a) Construct a 90% confidence interval for the true mean using the FPCF. (Round your answers to 4 decimal places.)
The 90% confidence interval is from _?_ to _?_
(b) What sample size would be needed for an error of ± 1.5 with 90% confidence? (Enter your answer as a whole number (no decimals). Use a z-value taken to 3 decimal places in your calculations.)
b. Sample size_??___