Voltage sags and swells. Refer to the Electrical Engineering

(Vol. 95, 2013) study of power quality (measured by “sags”

and “swells”) in Turkish transformers, Exercise 2.127

(p. 110). For a sample of 103 transformers built for heavy industry, the mean and standard deviation of the number of sags per week were 353 and 30, respectively; also, the mean and standard deviation of the number of swells per week were 184 and 25, respectively. Consider a transformer that has 400 sags and 100 swells in a week.

a. Would you consider 400 sags per week unusual statistically?

Explain.

b. Would you consider 100 swells per week unusual statistically?

Explain.