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A variable x of a finite population has the following frequency distribution :

x578
f254060

Suppose a member is selected at random from the population and let X denote the value of the variable x for the member obtained.

a. Determine the probability distribution of the random variable X.

b. Use random-variable notation to describe the events that X takes on the value 6, a value of at most 6, and a value greater than 6.

c. Find P(X = 6), P(X < 6), and P(X > 6). Interpret your results.

d. Construct a probability histogram for the random variable X.

Short Answer

Expert verified

Part a.

Random Variable

Probability

5

0.2

7

0.32

8

0.48

Part b.

On the value of 6: X = 6

A value of at most 6: X ≤ 6

A value greater than 6: X > 6

Part c.

P(X=6)=0P(X≤6)=0.2P(X>6)=0.8

Part d.

Step by step solution

01

Part (a) Step 1. Given information

The frequency distribution of a variable x in a finite population is as follows :

x

5

7

8

f

25

40

60

Let X signify the value of the variable x for the member acquired if a member is chosen at random from the population.

02

Part (a) Step 2. Formula Used

The experiment is conducted out assuming that the random variable (X=x) occurs n times out of a total of N times. As a result of the fNrule:

P(X=x)=nN

03

Part (a) Step 3. Solution

Here, N=25+40+60=125. Hence the probability of random variable X is:

Random Variable

Probability

5

25/125 = 0.2

7

40/125 = 0.32

8

60/125 = 0.48

04

Part (b) Step 1. Solution 

Event where X takes the value 2, can also be written as:

X = 6

Event where X takes a value of at most 2, can also be written as :

X ≤ 6

Event where X takes a value greater than 2, can also be written as :

X > 6

05

Part (c) Step 1. Solution

From the table,

P(X=6)=0P(X≤6)=0.2P(X>6)=0.32+0.48=0.8

06

Part (d) Step 1. Solution

The probability histogram for the random variable X is as follows:

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