1. The following are random data from a normal population.

3.3 3.3 4.7 2.6 6.4 4.7 1.7 4.5 5.0 3.0

Construct a 98% con?dence interval for the population mean μ.

2. The following data represent the rates (micrometers per hour) at which a razor cut made in the skin of anesthetized newts is closed by new cells.

28 20 21 39 32 23 18 31 14 23
18 22 28 24 33 12 23 21 25 25

(a) Can we say that the data are approximately normally distributed?

(b) Find a 95% con?dence interval for population mean rate μ for the new cells to close a razor cut made in the skin of anesthetized newts.

(c) Find a 99% con?dence interval for μ.

(d) Is the 95% CI wider or narrower than the 99% CI? Brie?y explain why.