Voltage and Insulating Fluid. Researchers examined the time in minutes before an insulating fluid lost its insulating property. The following data are the breakdown times for eight samples of the fluid, which had been randomly allocated to receive one of two voltages of electricity:
Times (min) at 26 kV: 5.79 1579.52 2323.70
Times (min) at 28 kV: 68.8 108.29 110.29 426.07 1067.60
(a) Form two new variables by taking the logarithms of the breakdown times: Y1 D log breakdown time at 26 kV and Y2 D log breakdown time at 28 kV.
(b) By hand, compute the difference in averages of the log-transformed data: Y 1 - Y 2.
(c) Take the antilogarithm of the estimate in (b): exp.Y 1 - Y 2/. What does this estimate? (See the interpretation for the randomized experiment model in Section 3.5.2.)
(d) By hand, compute a 95% confidence interval for the difference in mean log breakdown times. Take the antilogarithms of the endpoints and express the result in a sentence.