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

To find the grand mean, we need to calculate the average of all the observations. Adding up the ages of all the vehicles and dividing by the total number of vehicles gives us:
((2+6+10+8+7+11+5+6+9)/9) + ((6+9+10+11+7+8)/6) + ((5+8+6+10+4)/5) = 72/9 + 51/6 + 33/5 = 8.0. Therefore, the grand mean is 8.0.