EC507—Statistics for Economists
Sprimg 2010
Problem Set 4
1.
X
is a normally distributed random variable with mean equal to 7 and variance
equal to 25. You draw a random sample of size 100.
a.
Calculate
)
8
6
(
≤
≤
X
P
and
)
8
6
(
≤
≤
X
P
.
b.
Explain intuitively why the two probabilities differ.

This
** preview**
has intentionally

**sections.**

*blurred***to view the full version.**

*Sign up*
2.
Each minute a machine produces a length of rope with mean of 4 feet and
standard deviation of 5 inches. Assuming that the amounts produced in different
minutes are independent and identically distributed, approximate the probability
that the machine will produce at least 250 feet in one hour.