The alternating current (AC) breakdown voltage of an insulating liquid indicates its dielectric strength. The article "Testing Practices for the AC Breakdown Voltage Testing of Insulation Liquids" gave the accompanying sample observations on breakdown voltage (kV) of a particular circuit under certain conditions.

62 50 53 57 41 53 55 61 59 64 50 53 64 62 50 68
54 55 57 50 55 50 56 55 46 55 53 54 52 47 47 55
57 48 63 57 57 55 53 59 53 52 50 55 60 50 56 58

a) Construct a boxplot of the data and comment on interesting features.

b) Calculate and interpret a 95% Confidence Interval for true average breakdown voltage μ. Does it appeas that μ has been precisely estimated? Explain.

c) Suppose the investigator believes that virtually all values of breakdown voltage are between 40 and 70. What sample size would be appropriate for the 95% Confidence Interval to have a width of 2kV (so that μ is estimated to within 1 kV with 95% confidence?)