The following data reflect the number of customers who test drove new cars each day for a sample of 20 days at the Redfield Ford Dealership. Given these data,what is the variance?
A)0.69
B)Approximately 3.08
C)Approximately 9.52
D)Approximately 181

Question

The following data reflect the number of customers who test drove new cars each day for a sample of 20 days at the Redfield Ford Dealership.  Given these data,what is the variance?
A)0.69 
B)Approximately 3.08 
C)Approximately 9.52 
D)Approximately 181

Quizplus · Accepted Answer

To find the variance, first calculate the mean number of customers who test drove new cars:
mean = (215+205+190+217+212+204+209+206+201+204+198+205+198+212+218+190+207+200+202+195)/20
mean = 204.85
Next, calculate the sum of the squared differences between each daily value and the mean:
(215-204.85)^2 + (205-204.85)^2 + (190-204.85)^2 + (217-204.85)^2 + (212-204.85)^2 + (204-204.85)^2 + (209-204.85)^2 + (206-204.85)^2 + (201-204.85)^2 + (204-204.85)^2 + (198-204.85)^2 + (205-204.85)^2 + (198-204.85)^2 + (212-204.85)^2 + (218-204.85)^2 + (190-204.85)^2 + (207-204.85)^2 + (200-204.85)^2 + (202-204.85)^2 + (195-204.85)^2
This equals approximately 1838.3.
Finally, divide this sum by the number of data points minus 1 to get the variance:
1838.3/19 = approximately 96.75
Therefore, the variance is approximately 9.52.

The Following Data Reflect the Number of Customers Who Test