Refer to the Electrical Engineering (March 2013) assessment of the quality of electrical power, Exercise 5.37. Recall that a measure of quality is the degree to which voltage fluctuations cause light flicker in the system. The perception of light flicker Y in a system (measured periodically over 10-minute intervals) follows (approximately) a normal distribution with μ = 2.2% and σ = .5% Consider a random sample of 35 intervals.

a. Use statistical software to find the exact probability that the sample standard deviation, S, is less than .75%. 

b. If S = .4% use statistical software to find the exact probability that the sample mean perception of light flicker over the 35 sample intervals exceeds 2%.

Data from Exercise 5.37

An assessment of the quality of the electrical power system in Turkey was the topic of an article published in Electrical Engineering (March, 2013). One measure of quality is the degree to which voltage fluctuations cause light flicker in the system. The perception of light flicker Y when the system is set at 380 kV was measured periodically (over 10-minute intervals).