Question

CCA has stated in 2017 that 36.5 % of its students are first generation college students.Suppose you sample 15 CCA students and ask if they are first generation college students or not, counting the number of first generation students.

a. Create a binomial probability distribution (table) for this situation.
k P(X = k)
0
1
2
3
4
5
b. Give the mean of the binomial distribution. $
c. Give the standard deviation of this binomial distribution.
d. Compute the z-score for the outcome x = 2 students are the first generation.

Answer 1

Explanation:

The formula for binomial distribution is expressed as

P(x = r) = nCr × p^r × q^(n - r)

Where

x represent the number of successes.

p represents the probability of success.

q = (1 - p) represents the probability of failure.

n represents the number of trials or sample.

From the information given,

p = 36.5% = 36.5/100 = 0.365

q = 1 - p = 1 - 0.365

q = 0.635

n = 15

a) P(x = 0) = 15C0 × 0.365^0 × 0.635^(15 - 0) = 0.0011

P(x = 1) = 15C1 × 0.365^1 × 0.635^(15 - 1) = 0.0095

P(x = 2) = 15C2 × 0.365^2 × 0.635^(15 - 2) = 0.038

P(x = 3) = 15C3 × 0.365^3 × 0.635^(15 - 3) = 0.095

P(x = 4) = 15C4 × 0.365^4 × 0.635^(15 - 4) = 0.16

P(x = 5) = 15C5 × 0.365^5 × 0.635^(15 - 5) = 0.21

k P(X = k)

0 0.0011

1 0.0095

2 0.038

3 0.095

4 0.16

5 0.21

b) mean = np = 15 × 0.365 = 5.475

c) standard deviation = √npq

= √15 × 0.365 × 0.635

= 1.86

d) z = (x - mean)/standard deviation

x = 2

z = (2 - 5.475)/1.86 = - 1.87