**King Fahd University of Petroleum & Minerals**

**Mathematical Sciences**

**Stat319-Term033**

** Quiz #4 Sections: 3
& 4**

**Name:
ID: Serial:**

__Question one: (5 points)____ __

A
class consists of 20 students, 8 of them practice morning sport. If a sample of 4 different students is
selected at random.

a.
What is
the probability that at least three of them practice morning sport?

Solution:

_{}

b.
What is
the expected value of the number of the students who don’t practice the morning
sport?

Solution:

In
this case, consider _{}

_{}

__Question two: (5 points)__

A
school of 190 students take a certain exam.
A sample of size 40 students is selected at random from this
school. If the standard deviation of the
marks of the 190 students in this school was 1.5 then

a.
What is the
sampling distribution for the sample mean _{}

Solution:

_{}

b.
What is the
probability that _{} will lie within two
standard deviations form it’s mean?

_{}