**MATH 221 Statistics for Decision Making ****Week 3 Homework **

MATH 221 Statistics for Decision Making Week 3 Homework

Question 1Let x represent the number of cars in a parking lot. This would be considered what type of variable:

Nonsensical

Continuous

Lagging

Question 2 Let x represent the inches of rain on crops in Akron, Ohio. This would be considered what type of variable:

Continuous

Discrete

Inferential

Distributed

Question 3Consider 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?

42.5%

23.7%

18.9%

16.5%

Question 4Consider the following table.

Weekly hours worked Probability

1-30 (average=23) 0.08

31-40 (average=36) 0.10

41-50 (average=43) 0.74

51 and over (average=54) 0.08

Find the mean of this variable.

39.0

31.8

41.6

25.2

Question 5Consider 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.

0.85

1.44

1.35

1.83

Question 6Consider the following table.

Defects in batch Probability

2 0.18

3 0.29

4 0.18

5 0.14

6 0.11

7 0.10

Find the standard deviation of this variable.

2.49

4.01

1.58

1.52

Question 7The standard deviation of samples from supplier A is 0.0841, while the standard deviation of samples from supplier B is 0.0926. Which supplier would you be likely to choose based on these data and why?

Supplier A, as their standard deviation is higher and, thus easier to fit into our production line

Supplier A, as their standard deviation is lower and, thus, easier to fit into our production line

Supplier B, as their standard deviation is lower and, thus, easier to fit into our production line

Supplier B, as their standard deviation is higher and, thus, easier to fit into our production line

Question 8Ten fourth graders are randomly selected. The random variable represents the number of fourth graders who own a smartphone. For this to be a binomial experiment, what assumption needs to be made?

The probability of being selected is the same for all fourth graders

The probability of owning a smartphone is the same for all fourth graders

All ten selected fourth graders are the same age

The probability of being a fourth grader is the same for all those selected

Question 9A survey found that 39% of all gamers play video games on their smartphones. Ten frequent gamers are randomly selected. The random variable represents the number of frequent games who play video games on their smartphones. What is the value of n?

0.10

x, the counter

10

0.39

Question 10

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) 0.207 (2) 0.901

(1) 0.793 (2) 0.099

(1) 0.762 (2) 0.901

(1) 0.207 (2) 0.099

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