Answer :
Answer:
A. 0.2734 = 27.34% probability that there are an equal number of boys and girls
B. 0.2753 = 27.53% probability that she’ll answer exactly 5 questions correctly
Step-by-step explanation:
In each of these questions, the binomial probability distribution is used.
Binomial probability distribution
The binomial probability is the probability of exactly x successes on n repeated trials, and X can only have two outcomes.
[tex]P(X = x) = C_{n,x}.p^{x}.(1-p)^{n-x}[/tex]
In which [tex]C_{n,x}[/tex] is the number of different combinations of x objects from a set of n elements, given by the following formula.
[tex]C_{n,x} = \frac{n!}{x!(n-x)!}[/tex]
And p is the probability of X happening.
A.The Murray family has produced 8 children.
What is the probability that there are an equal number of boys and girls?
8 children means that [tex]n = 8[/tex]
Each children is equally as likely to be a boy or a girl, which means that [tex]p = 0.5[/tex]
This probability is P(X = 4). So
[tex]P(X = x) = C_{n,x}.p^{x}.(1-p)^{n-x}[/tex]
[tex]P(X = 4) = C_{8,4}.(0.5)^{4}.(0.5)^{4} = 0.2734[/tex]
0.2734 = 27.34% probability that there are an equal number of boys and girls
B.Margie has the uncanny ability of being able to guess the correct answer to TRUE/FALSE questions with an 80% accuracy rate. Tomorrow’s test has 7 questions on it and she needs to answer 5 questions correctly in order to make the Honor Roll. If she guesses on every question, what is the probability that she’ll answer exactly 5 questions correctly?
80% accurracy rate means that [tex]p = 0.8[/tex]
7 questions means that [tex]n = 7[/tex]
The probability is P(X = 5). So
[tex]P(X = x) = C_{n,x}.p^{x}.(1-p)^{n-x}[/tex]
[tex]P(X = 5) = C_{7,5}.(0.8)^{5}.(0.2)^{2} = 0.2753[/tex]
0.2753 = 27.53% probability that she’ll answer exactly 5 questions correctly