AutoTrader.com would like to test if a difference exists in the age of three different types of vehicles currently on the road: trucks, cars, and vans. The following data represent the age of a random sample of trucks, cars, and vans. The grand mean for these observations is ________.
A) 7.2
B) 8.0
C) 8.9
D) 9.3

Question

AutoTrader.com would like to test if a difference exists in the age of three different types of vehicles currently on the road: trucks, cars, and vans. The following data represent the age of a random sample of trucks, cars, and vans.  The grand mean for these observations is ________.
A) 7.2 
B) 8.0 
C) 8.9 
D) 9.3

Quizplus · Accepted Answer

The grand mean can be found by taking the average of all the observations. Adding up all the ages and dividing by the total number of observations (30) gives a grand mean of 8.0.