Statistics quiz 12 problems
josran
stat200_quiz1.docxSTAT 200 QUIZ 1 Section 6380 Fall 2014
I have completed this assignment myself, working independently and not consulting anyone except the instructor.
NAME_____________________________
INSTRUCTIONS
· The quiz is worth 40 points total.
· The quiz covers Chapters 1, 2 and 3.
· Make sure your answers are as complete as possible and show your work/argument. In particular, when there are calculations involved, you should show how you come up with your answers with critical work and/or necessary tables. Answers that come straight from program software packages will not be accepted.
(For Questions 1 to 7) The checkout times (in minutes) for 12 randomly selected customers at a large supermarket during the store’s busiest time are as follows:
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4.5 |
8.5 |
6.0 |
8.0 |
11.0 |
9.5 |
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12.5 |
6.5 |
10.0 |
9.0 |
6.5 |
13.0 |
1. (2 points) (Show work) What is the mean checkout times based on the 12 checkout times. (Round the answers to two decimal places)
2. (5 points) (Show work) Give a 5-number summary of the checkout time. (Round the answers to two decimal places)
3. (4 points) Prepare a frequency distribution with a class width of 2 minutes (with the first class as 4.0 – 5.9, etc.).
4. (2 points) (Show work) Identify the class midpoints for frequency distribution from Question 3. (Round the answers to two decimal places)
5. (3 points) (Show work) Construct the relative frequency distribution based on the frequency distribution from Question 3. (Round the percentage to one decimal place)
6. (3 points) (Show work) We usually find the mean checkout time based on the raw data. Now suppose that we don’t have the raw data, but instead, we only have the frequency distribution. Find the mean checkout time based on the frequency distribution from Question 3. (Round the answer to two decimal places) Compare your results with the "actual" mean checkout time you found in Question 1.
7. (5 points) (Show work) Find the standard deviation of the checkout time based on the frequency distribution from Question 3. Please show your calculation in the following table. (Round the answer to two decimal places)
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Check-out time |
Frequency f |
Mid-point x |
x2 |
f * x2 |
f * x |
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4.0 – 5.9 |
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(For Questions 8, 9 & 10) To qualify for a mortgage, an applicant needs to have a good FICO credit score. We chose a random sample of 6 applicants from a local bank, and their FICO scores are 715, 750, 665, 820, 550 and 610.
8. (5 points) (Show work) What is the standard deviation of the FICO scores in the sample? Please show your calculation in the following table; you may not need all columns based on the formula you use. (Round the answer to two decimal places)
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FICO Score x |
x2 |
x-mean |
(x-mean)2 |
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715 |
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750 |
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665 |
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820 |
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550 |
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610 |
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( Sum ) |
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9. (2 points) (Show work) Are any of these FICO scores considered unusual in the sense of our textbook? Explain.
10. (2 points) (Show work) What is the coefficient of variation in FICO scores of the sample? (Round the answer to two decimal places)
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11. (4 points) Determine whether the given value is a parameter or statistics. Please explain your answer.
(a) An agency conducts a survey on the choice of vegetable by Americans. It is reported by the agency that 57% of the respondents prefers broccoli.
(b)A UMUC STAT 200 instructor randomly selected 100 students and found the average study time is 20.5 hours per week.
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12. (3 points) Mimi is a recent college graduate, who is considering some career opportunities. One factor that will affect her decision is how much money she is likely to make. She got salary information from Internet. Since you are taking a Statistics course, she would like to get your opinion on whether mean salary or median salary information is more useful for her. What would be your recommendation? Please explain your answer.
