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1. Which of the following would “most likely” be a better measure of a set of observations describing the incomes of a population?

A. the mean

B. the median

C. the mode

D. the range

Incomes may be skewed to right or left. So mean isn’t appropriate, median is.

Use the following information to answer questions 2-10:

Over the last two months, I have recorded the lengths of time (in minutes) that I have had to wait to find a parking space at my local Costco. They are the following:

1.5 .5 2.5 4.0 3.2 2.0 4.3 2.4 1.75 0.0

2. Compute the mean time that I have had to wait to find a parking space over the last two months.

A. 2.00 minutes

B. 2.46 minutes

C. 2.77 minutes

D. 2.22 minutes

Mean µ = Σx/n = (1.5+.5+2.5+4+3.2+2+4.3+2.4+1.75+0.0)/10 = 2.22

3. Compute the median time that I have had to wait to find a parking space over the last two months.

A. 2.0 minutes

B. 2.20 minutes

C. 2.22 minutes

D. 2.40 minutes

Arrange in increasing order and take the average of middle two values (5th and 6th value).

0.0, 0.5, 1.5, 1.75, 2, 2.4, 2.5, 3.2, 4, 4.3

Median = (2+2.4)/2 = 2.2

4. The variance of my mean wait time for a parking space at Costco is:

A. 4.15

B. 1.72

C. 1.31

D. 17.24

Variance = (Σ(x-µ)²)/n = ((1.5-2.2)^2+(.5-2.2)^2+(2.5-2.2)^2+(4-2.2)^2+(3.2-2.2)^2+(2-2.2)^2+(4.3-2.2)^2+(2.4-2.2)^2+(1.75-2.2)^2+(0.0-2.2)^2)/10

= 1.72

5. By the way, how many times have I visited Costco in the last two months?

A. 10

B. 9

C. unknown, because this is a sample of the number of times that I have really visited

D. 8, due to (n-1) degrees of freedom

Count n = 10

6. Using the data above, what is the probability that the next time I visit Costco, I will be able to find a parking space in 1.5 minutes?

A. 15 percent

B. 1.5 percent

C. 10 percent

D. 90 percent

Probability = Number of times 1.5 occur / Total number of times = 1/10 = 10%

7. The data above can best be described by a:

A. discrete probability distribution

B. continuous probability distribution

C. neither

Time is contiuous.

8. The distribution of my wait time for a parking space at Costco follows a normal distribution. What is the probability that next time I visit Costco, my wait time for a parking space will be less than 5 minutes?

A. 100%

B. 98%

C. 48%

D. 2.12%

P(x ................
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