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.

) Construct a 90 percent confidence interval for the true mean. (Round your answers to 2 decimal places.)

) Normality may be an issue here because:

• The sample size is very small
• The distribution is skewed
• The sample size is very big
• There are possible outliers

C) What sample size would be needed for an error of 1.5 with 98 percent confidence? (Round your answer to the nearest whole number.)