Math Answers

1.Let the random variable X be the total number of heads when a fair coin is tossed 4 times.

•Is this a Bernoulli or binomial trial/experiment?

•Are the conditions of a Binomial trial satisfied?

•Find the probability mass function for X.

2. The probability that the patient recovers from a rare blood disease is 0.4. If 10 people are known to have contracted the disease, what is the probability that

a) exactly 3 patients survive the disease?

b) from 3 to 5 patients survive the disease?

3. Suppose that a student is given a test with 10 true-false questions. Let X be the number of questions guessed correctly by the student.

i) Write down the probability distribution (probability mass function) of X

ii) What is the probability that the student guesses all questions correctly?

iii) what is the probability that is the probability that the student guesses 7 or more questions

correctly?

FIND THE MEAN OF THE SET OF DATA BELOW AND CONSTRUCT A SAMPLING DISTRIBUTION

BY SELECTING 3 SAMPLES AT A TIME: 7 10 14 17 20

The distribution function of a discrete random variable X is given by

F_x(k) = "\\begin{Bmatrix}\n 0, & k < 1 \\\\\n 0.1, & 1 \\leq k <2 \\\\\n 0.3, & 2 \\leq k <3\\\\\n0.7, & 3 \\leq k <4 \\\\\n0.8 & 4 \\leq k < 5\\\\\n1 & k \\geq 5\n\\end{Bmatrix}"

1) What are the possible values of X?

2) Find the probability mass function of X.

Suppose that 4 children are planned in a family. Let the random variable X stand for the number of boys. Discuss the probability distribution of X.

• Find the mean and variance of the random variable X.

Consider the experiment of throwing a pair of dice. We are interested in the sum of the two numbers that occur. We know that X can assume the numbers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, and 12.

1) What is the probability mass function of X?

2) What is the probability that the number of dots will be at least 4 and at most 7?

3) Find the probability that the sum will be at least 7.

Suppose that a couple in planning 3 children is primarily interested in the number of boys.

1) - Define the random variable X.

2) - What is the range of X?

3) - Find the probability function of X.

4) - Find the probability mass function

5) - Draw the graph for the probability mass function

Suppose that a pair of fair dice is thrown 1 time. Let the random variable X be the absolute difference of the dots that appear.

1) - What are the possible values of X?

2) - What is the sample space?

3) - Find the probability functions of X.

4) - Find the probability mass function

5) - Draw the graph for the probability mass function

In an experiment of rolling a balanced die twice, let X be the maximum of the two numbers obtained.

1) What are the possible values of X?

2) Write down the sample space

3) Wat is the probability function for X?

4) Determine and sketch the probability mass function of X.

5) Find the expected value of X.

6) Find the variance of X.

A contractor has submitted bids for two state construction projects. The probability that he will be awarded any contract is 0.3 and it is the same for each of the two contracts.

1) - What is the probability that he will be awarded both contracts?

2) - What is the probability that he will be awarded neither contract?

In a class, 70% of all students are boys and the rest are girls.

• 10% of the girls are smokers

• 20% of the boys are smokers

1) Find the probability that a randomly selected student is a smoker.