week 8 carmen quiz: discrete random variables

The mean cost of a box of Cheerios Oat Crunch is $4.00 and the variance is .35. If the price increases by 25 cents a box, what is the new variance?

.35

Let X = time waiting in line at a restaurant to get a seat. Mean of X = 20 min, Variance of X = 25 Let Y = time waiting for your food to arrive. Mean of X = 30 min, Variance of Y = 36 X and Y are correlated and the correlation is 0.80. What is the variance of the TOTAL TIME waiting?

109

X12p(x).5.5 What is the variance of X?

.25

X123p(x).1.3.6 What is the probability that X is at least 2?

0.90

Suppose X = number of 1 foot long steps taken in one hour by a person working in a bank. Suppose the mean of X is 300 and the variance is 64. If you change the units from feet to inches, you multiply by 12. What is the new standard deviation?

Square root of (12^2 x 64)

Suppose X and Y are independent. Then is the following true or false? sigmax+y = sigmax + sigmay

false

X123p(x)1/21/41/4 True/False: The mean of X is 2.

false

If X and Y are independent, then True/False: Variance of (X-Y) = Variance of (Y-X)

true

True or False? Mx-y = Mx - My

true

True or False? Suppose X and Y are independent. Then is the following TRUE or FALSE? Sigma/squared(x-y) = sigma/squaredx + sigma/squaredy

true