Consider a binomial experiment with 15 trials and probability 0.45 of success on

geduiwelh

geduiwelh

Answered question

2021-09-21

Take a look at experiment with 15 trials and probability 0.45 of success on a single trial. 
(a) Use the binomial distribution to find the probability of exactly 10 successes.
(b) Use the normal distribution to approximate the probability of exactly 10 successes.

Answer & Explanation

coffentw

coffentw

Skilled2021-09-22Added 103 answers

Step 1
Solution: It is given here that a random variable say x follows the binomial distribution with parameters n=15 and p=0.45
The binomial probability function is:
P(X=x)=n!(nx)!x!px(1p)nx;x=0,1,2,..,n
Step 2
(a) Use the binomial distribution to find the probability of exactly 10 successes.
Answer: It is required to find:
P(x=10)
Using the binomial distribution function:
P(x=10)=15!(1510)!10!0.4510(10.45)1510
=3003×0.000340506×0.050328438
=0.051
Therefore, the probability of exactly 10 successes is 0.051
Step 3
(b) Use the normal distribution to approximate the probability of exactly 10 successes.
Answer:
The mean and standard deviation of the random variable x is:
μ=np=15×0.45=6.75
σ=np(1p)=15×0.45(10.45)=1.92678
It is required to find:
P(x=10)
Using the continuity correction factor, the above probability can be written as:
P(x=10)=P(100.5<x<10+0.5)
=P(9.5<x<10.5)
Using the z-score formula:
P(9.5<x<10.5)=P(9.56.751.92678<xμσ<10.56.751.92678
=P(1.4272<z<1.9462)
=P(z<1.9462)P(z<1.4272)
Now using the excel functions:
P(9.5<x<10.5)=P(z<1.9462)P(z<1.4272)=0.97420.9232=0.051
The excel functions are:
=NORMSDIST(1.4272)=0.9232
=NORMSDIST(1.9462)=0.9742
Therefore, Using the normal distribution to approximate the probability of exactly 10 successes is 0.051

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