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Lesson 5.1 Probability Model Homework Due 2/1 PM

Last updated over 1 year ago

9 questions

Note from the author:

This is for a daily grade, use it to make sure you understand Lesson 5.1.

Instructions

This is for a daily grade, use it to make sure you understand Lesson 5.1.

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Question 1

1.

Choose a person aged 19 to 25 years at random and ask, “In the past seven days, how many times did you go to an exercise or fitness center or work out?” Call the response Y for short. Based on a large sample survey, here is a probability model for the answer you will get.

What will you check to determine if this is a valid probability model?
Choose all correct answers.

No probability is larger than 0.70

The probabilities add up to 1.00

The probabilities add up to 1.05

Probabilities are all decimals between 0 and 1, inclusive.

Probabilities are all decimals between 0 and 1, not inclusive.

The probabilities add up to 0.95

Question 2

2.

Use the information from #1:
Describe the event Y < 3 in words.
What is P(Y < 3)?
Choose both correct answers.

P(Y<3)=0.80

P(Y<3)=0.88

P(Y<3)=0.12

The probability that a person works out no more than three days in one week.

P(Y<3)=0.20

The probability that a person works out at least three days in one week.

The probability that a person works out less than three days in one week.

Question 3

3.

Spell-checking software catches “nonword errors,” which result in a string of letters that is not a word, as when “the” is typed as “teh.” When undergraduates are asked to write a 250- word essay (without spell-checking), the number X of nonword errors in a randomly selected essay has the following distribution.

Find the missing value for P(X = 2) in the probability distribution.
Enter your answer as a decimal.

Question 4

4.

a. Write the event “at least 1 non-word error” in terms of X.

b. What is the probability of this event?

Choose both correct answers.

0.7

P(X<1)

P(X<1)

0.1

0.3

P(X>1)

P(X>1)

0.9

Question 5

5.

Find P(X > 1).

Question 6

6.

You just found P(X > 1). Now choose why this answer is different from the answer in #4.

There is not difference between the two probabilities.

The probability of getting one nonword error is included in the answer.

The probability of getting one nonword error is not included in the answer.

Question 7

7.

Discrete or continuous? Classify each of the following random variables as discrete or continuous.

W = the exact amount of sleep that a randomly selected student from your school got last night
R = the number of times you have to roll a fair, six-sided die to get a 1
T = winning time in the men’s 100-meter dash at a randomly selected international track meet
X = the pH of a water sample that has been randomly selected from a stream
Y = the number correct on a recent multiple-choice test for a randomly selected student in your class

Discrete Variable
Continuous Variable

Question 8

8.

According to a recent survey, 67% of cell-phone owners find themselves checking their phone for messages, alerts, or calls—even when they don’t notice their phone ringing or vibrating.
Suppose we randomly select 5 cell-phone owners at random.

Find the probability that all 5 cell-phone owners check their phones even when the phone doesn’t ring or vibrate.
Round your answer to three places past the decimal.

Question 9

9.

According to a recent survey, 67% of cell-phone owners find themselves checking their phone for messages, alerts, or calls—even when they don’t notice their phone ringing or vibrating.
Suppose we randomly select 5 cell-phone owners at random.

What’s the probability that at least 1 of them doesn’t check the phone?
Hint: use the information from #8.