Question: A random sample of 21 nickels measured with a very accurate micrometer showed a mean diameter of 0.834343 inches with a standard deviation of 0.001886 inches.

(a) Why would nickel diameters vary?

(b) Construct a 99 percent confidence interval for the true mean diameter of a nickel.

(c) Discuss any assumptions that are needed.

(d) What sample size would ensure an error of ± 0.0005 inches