The following is the frequency distribution for the speed of a sample of automobiles traveling on an interstate highway. The standard deviation is
A) 9.06.
B) 9.28.
C) 86.19.
D) 82.09.

Question

The following is the frequency distribution for the speed of a sample of automobiles traveling on an interstate highway.  The standard deviation is
A) 9.06. 
B) 9.28. 
C) 86.19. 
D) 82.09.

Quizplus · Accepted Answer

To calculate the standard deviation, we need to first calculate the mean:

(50*60 + 60*70 + 70*52 + 80*28 + 90*10)/220 = 63.45

Now we can use the formula for the standard deviation:

sqrt(((50-63.45)^2*60 + (60-63.45)^2*70 + (70-63.45)^2*52 + (80-63.45)^2*28 + (90-63.45)^2*10)/219)

Simplifying this expression gives a standard deviation of approximately 9.28, which corresponds to choice B.

The Following Is the Frequency Distribution for the Speed of a Sample