Question

In a certain town, 22% of voters favor a given ballot measure. for groups of 21 voters, find the variance for the number who favor the measure.
a. 1.9
b. 13
c. 4.6
d. 3.6

Answer 1

c. 4.6
       
21 X .22= 4.6
       
Calculating the variance requires finding the product of 21 and 22%. To make this easier we convert 22% into it's decimal form and construct the equation. To back check this answer we can use 10% of 21 voters which equals 2.1% then double that amount to reach 4.2%, knowing that we now have a close approximation of the variance we can eliminate answers a, b, and d, leaving c as the only logical choice.