Question

A six-sided and a ten-sided die are both rolled. The mean and std dev for the six-sided die are $3.5$ and $1.707$. For the ten-sided die the mean and std dev are $5.5$ and $2.872$. If the results of the two dice are added, find the variance if the results of the six-sided die is subtracted from the result of the ten-sided die.

• A. $3.345$
• B. $3.341$
• C. $2.545$
• D. None of these

Answer 1

Answer: (B)

$3.341$

Given that the std dev for the six-sided die is $1.707$

The std dev of the ten-sided die is $2.872$

Therefore, total std dev is $\sqrt{{1.707}^2+{2.872}^2}=3.341$

The standard deviation doesn't change if the results are subtracted.