Question

A physician would like to know the mean fasting blood glucose value (milligrams per
100 ml) of patients seen in a diabetes clinic over the past 10 years. Determine the number
of records the physician should examine in order to obtain a 90% confidence interval for
µ if the desired width of the interval is 6 units (SE = 3) and a pilot sample yields a
variance of 60. Show all work or no credit will be received.

13. A physician would like to know the mean fasting blood glucose value (milligrams per 100 ml) of patients seen in a diabetes clinic over the past 10 years. Determine the number of records the physician should examine in order to obtain a 90% confidence interval for u if the desired width of the interval is 6 units (SE = 3) and a pilot sample yields a variance of 60.

Answer 1

We have sample variance given and we have to find the interval for population mean with unknown population SD, so we will use a t-dist.

90% confidence interval for population mean is given by

(3 - t-1,0 10/2 * SE,T+ -1,0, 10/2 * SE)

Width =

1 + tn-1.0.10/2 * SE - (1 -tn-1.0.10/2 * SE)

6 =

2tn-1,0.10/2 * SE

We have Std error SE = 3

tn-1,0,05 = 23

= 1

Looking in the t-dist tables with for x = 1 under p = 0.05