Two investigators tested their friends for memory span. The first tested five people and found a mean of 6.0. The second tested nine people and found a mean of 7.0. The weighted mean for the data is
A) 6.00
B) 6.50
C) 6.64
D) 7.00.

Question

Quizplus · Accepted Answer

The weighted mean is calculated by multiplying each group's mean by the number of observations in that group, summing these products, and then dividing by the total number of observations. For the first group: 5 people * 6.0 = 30. For the second group: 9 people * 7.0 = 63. The total is 93, and the total number of people is 14 (5+9). So, the weighted mean = 93 / 14 = 6.64.

Two Investigators Tested Their Friends for Memory Span