Ten percent of American adults are left-handed. Suppose we have a sample of 25 people. Assume that each person in the sample is either left or right-handed.

a) Find the meanand standard deviationfor the number of left-handed people in the sample.

Mean= 2.5 standard deviation = 1.5

b) Would it be unusual to surveya group of 25 people and find that 7 of them are left-handed? Explain.

a)

n = 25, p = 0.1, q = 1 – 0.1 = 0.9

Mean = np = 25*0.10 = …

The expert examines mean, standard deviation for numbers of left-handed people.