Dr. Susan Benner is an industrial psychologist. She is currently studying stress among executives of internet companies. She has developed a questionnaire that she believes measures stress. A scope above 80 indicates stress at a dangerous level. A random sample of 15 executives revealed the following stress level scores.

Stress Level Scores

94

78

83

90

78

99

97

90

97

90

93

94

100

75

84

(a) What is estimate of the population mean?

(b) Develop a 90 percent confidence interval for the population mean.

(c) Interpret the results in part b.

(d) Is it reasonable to conclude that Internet executives have a mean stress level in the dangerous level, according to the results of Dr. Benner's study?