# What percentage of the checkout timesas less than 3 minutes

August 31, 2017

Question
Checkout Time (in minutes) Frequency
1.0 – 1.9 5
2.0 – 2.9 6
3.0 – 3.9 4
4.0 – 4.9 3
5.0 – 5.9 2
1. What percentage of the checkout timesas less than 3 minutes?

2. Calculate the mean of this frequency distribution.
3. Calculate the standard deviation of this frequency distribution.
4. Assume that the smallest observation in this dataset is 1.2 minutes. Suppose this observation were incorrectly recorded as 0.12 instead of 1.2. Will the mean increase, decrease, or remain the same? Will the median increase, decrease or remain the same?

A 6-faced die is rolled two times. Let A be the event that the outcome of the first roll is greater than 4. Let B be the event that the outcome of second roll is an odd number.
5. What is the probability that the outcome of the second roll is an odd number, given that the first roll is greater than

4?
6. Are A and B independent? Why or why not?

A random sample of STAT200 weekly study times in hours is as follows: 4 14 15 17 20
7. Find the standard deviation.
8. Are any of these study times considered unusual in the sense of our textbook? Explain. Does this differ with your intuition? Explain.

The table shows temperatures on the first 12 days of October in a small town in Maryland.
Date Temperature Date Temperature Date Temperature
Oct 1 73 Oct 5 53 Oct 9 66
Oct 2 66 Oct 6 52 Oct 10 49
Oct 3 65 Oct 7 62 Oct 11 53
Oct 4 70 Oct 8 55 Oct 12 57

9. Determine the five-number summary for this data.
10. Determine the mean temperature.
11. Determine the mode(s), if any.

Refer to the following table for Questions 9, 10, and 11. Show all work. Just the answer, without supporting work, will

There are 1000 students in the senior class at a certain high school. The high school offers two Advanced Placement math / stat classes to seniors only: AP Calculus and AP Statistics. The roster of the Calculus class shows 100 people; the roster of the Statistics class shows 80 people. There are 45 overachieving seniors on both rosters.
12. What is the probability that a randomly selected senior is in at least one of the two classes?
13. What is the probability that a randomly selected senior takes only one class?

A box contains 10 chips. The chips are numbered 1 through 10. Otherwise, the chips are identical. From this box, we draw one chip at random, and record its value. We then put the chip back in the box. We repeat this process two more times, making three draws in all from this box.
14. How many elements are in the sample space of this experiment?
15. What is the probability that the three numbers drawn are all multiples of 3?

x 2 3 4 5 6
P(x) 0.1 0.2 0.3 0.1 0.3
16. Determine the expected value of x.
17. Determine the standard deviation of x.

Consider the following situation for Questions 18, 19 and 20. Show all work. Just the answer, without supporting work, will receive no credit.
Mimi just started her tennis class three weeks ago. On average, she is able to return 15% of her opponent’s serves. Let random number X be the number of serves Mimi returns. As we know, the distribution of X is a binomial probability distribution. If her opponent serves 10 times, please answer the following questions:
18. What is the number of trials (n), probability of successes (p) and probability of failures (q), respectively? (5 pts)
19. Find the probability that she returns at least 2 of the 10 serves from her opponent . (10 pts)
20. Find the mean and standard deviation for the probability distribution. (10 pts)

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