Texts: Rounding rule for the Mean, Variance, and Standard Deviation for a
Probability Distribution
The mean, variance, and standard deviation for a probability distribution should be
rounded to one more decimal place than the outcome X.
Example #9: Find the mean, variance, and the standard deviation of the number of spots
that appear when a die is tossed. (Use the distribution from Example #2).
Outcome X
Probability P(X)
1
2
3
4
5
6
Probability P(X)
1/6
1/6
1/6
1/6
1/6
1/6
Example #10: A coin is tossed 3 times. Find the mean, variance, and the standard
deviation for the number of heads. (Use the distribution from Example #3).
Outcome X
Probability P(X)
0
1
2
3
Probability P(X)
1/8
3/8
3/8
1/8