# Math 221 – quizzes – week 3 homework

Question 1 2 pts
Let x represent the number of pets in pet stores. This would be considered what type of variable:
Discrete
Nonsensical
Continuous
Lagging
Question 2 2 pts
Let x represent sheets of paper in a package. This would be considered what type of variable:
Distributed
Continuous
Inferential
Discrete
Question 3 2 pts
Consider the following table.
Age Group Frequency
18-29           9831
30-39           7845
40-49           6869
50-59           6323
60-69           5410
70 and over 5279
If you created the probability distribution for these data, what would be the probability of 40-49?
16.5%
18.9%
23.7%
42.5%
Question 4 2 pts
Consider the following table.
Weekly hours   worked    Probability
1-30   (average=22)              0.08
31-40   (average=35)            0.16
41-50   (average=46)            0.72
51 and over   (average=61)  0.04
Find the mean of this variable.
39.0
40.2
35.9
41.0
Question 5 2 pts
Consider the following table.
Defects in   batch      Probability
0                                   0.28
1                                   0.35
2                                   0.16
3                                   0.09
4                                   0.10
5                                   0.02
Find the variance of this variable.
1.44
0.85
1.35
1.83
Question 6 2 pts
Consider the following table.
Defects in   batch      Probability
2                                 0.35
3                                 0.23
4                                 0.20
5                                 0.09
6                                 0.07
7                                 0.06
Find the standard deviation of this variable.
1.51
2.27
4.50
3.48
Question 7 2 pts
The standard deviation of the number of video game A’s outcomes is 05479, while the standard deviation of the number of video game B’s outcomes is 0.2498. Which game would you be likely to choose if you wanted players to have the most choice and why?
Game A, as   the standard deviation is higher and, thus offers fewer choices in outcomes
Game B, as   the standard deviation is lower and, thus offers more choices in outcomes
Game A, as   the standard deviation is lower and, thus offers fewer choices in outcomes
Game B, as   the standard deviation is higher and, thus offers more choices in outcomes
Question 8 2 pts
Thirty-five percent of teens buy soda (pop) at least once each week. Eleven kids are randomly selected. The random variable represents the number of these kids who purchase soda (pop) at least once each week. For this to be a binomial experiment, what assumption needs to be made?
The probability of being a teen and being a kid should be the same.
All teens have the same probability of being selected.
All the kids eligible to be selected are teens.
All eleven kids selected live in the same region.
Question 9 2 pts
A survey found that 31% of all teens buy soda (pop) at least once each week. Seven teens are randomly selected. The random variable represents the number of teens who buy soda (pop) at least once each week. What is the value of n?
x, the counter
0.07
0.31
7
Question 10 2 pts
Forty-four percent of US adults have little confidence in their cars. You randomly select twelve US adults. Find the probability that the number of US adults who have little confidence in their cars is (1) exactly six and then find the probability that it is (2) more than 7.
(1) 0.793 (2)   0.0099
(1) 0.207 (2)   0.901
(1) 0.762 (2)   0.901
(1) 0.207 (2)   0.099
Question 11 2 pts
Say a business wants to know if each salesperson is equally likely to make a sale. The company chooses 5 salespeople and gathers information on their sales experiences. What assumption must be made for this study’s probability results to be used in future binomial experiments?
That for every 5 salespeople, the probability of making a sale is the same
That the probability of each salesperson being one of the selected 5 is the same
That 5% is the correct probability to use in future studies
That the selected 5 have similar characteristics and sales areas as the other   salespeople
Question 12 2 pts
Eight baseballs are randomly selected from the production line to see if their stitching is straight. Over time, the company has found that 93.8% of all their baseballs have straight stitching. If exactly six of the eight have straight stitching, should the company stop the production line?
Yes, the   probability of six or less having straight stitching is unusual
No, the   probability of six or less having straight stitching is not unusual
No, the   probability of exactly six have straight stitching is not unusual
Yes, the   probability of exactly six having straight stitching is unusual
Question 13 2 pts
A soup company puts 20 ounces of soup in each can. The company has determined that 97% of cans have the correct amount. Which of the following describes a binomial experiment that would determine the probability that a case of 24 cans has all cans that are properly filled?
n=20, p=0.97,   x=20
n=24, p=0.97,   x=1
n=24, p=0.97,   x=24
n=20, p=0.97,   x=20
Question 14 2 pts
A supplier must create metal rods that are 18.1 inches width to fit into the next step of production. Can a binomial experiment be used to determine the probability that the rods are the correct width or an incorrect width?
No, as the   probability of being about right could be different for each rod selected
Yes, all   production line quality questions are answered with binomial experiments
No, as there   are three possible outcomes, rather than two possible outcomes
Yes, as each   rod measured would have two outcomes: correct or incorrect
Question 15 2 pts
In a box of 12 pens, there is one that does not work. Employees take pens as needed. The pens are returned once employees are done with them. You are the 5th employee to take a pen. Is this a binomial experiment?
No, binomial does not include systematic selection such as “fifth”
No, the probability of getting the broken pen changes as there is no replacement
Yes, you are find the probability of exactly 5 not being broken
Yes, with replacement, the probability of getting the one that does not work is the   same
Question 16 2 pts
Forty-two percent of employees make judgements about their co-workers based on the cleanliness of their desk. You randomly select 7 employees and ask them if they judge co-workers based on this criterion. The random variable is the number of employees who judge their co-workers by cleanliness. Which outcomes of this binomial distribution would be considered unusual?
1, 6, 7
1, 2, 6, 7
0, 6, 7
0, 1, 2, 7
Question 17 2 pts
Eighty-one percent of products come off the line within product specifications. Your quality control department selects 15 products randomly from the line each hour. Looking at the binomial distribution, if fewer than how many are within specifications would require that the production line be shut down (unusual) and repaired?
Fewer than 12
Fewer than 9
Fewer than 11
Fewer than 10
Question 18 2 pts
The probability of a potential employee passing a drug test is 86%. If you selected 12 potential employees and gave them a drug test, how many would you expect to pass the test?
8 employees
9 employees
10 employees
11 employees
Question 19 2 pts
The probability of a potential employee passing a training course is 86%. If you selected 15 potential employees and gave them the training course, what is the probability that more than 12 will pass the test?
0.852
0.900
0.648
0.352
Question 20 2 pts
Off the production line, there is a 3.7% chance that a candle is defective. If the company selected 45 candles off the line, what is the probability that fewer than 3 would be defective?
0.768
0.975
0.918
0.037