STAT 200 QUIZ 1 Section 6360 Fall 2017 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 Week 1 and Week 2 materials. Make sure your answers are as complete as possible and show your work/argument. When there are calculations involved, you should show how you come up with your answers with critical work and/or necessary tables. You must show why you choose certain answer for true-or-false and multiple choice questions. Answers that come straight from programs or software packages will not be accepted. The quiz is open book and open notes. This means that you may refer to your textbook, notes, and online course materials for the current course, but you must work independently and may not consult anyone except the instructor. The brief honor statement is on top of the exam. If you fail to put your name under the statement, your quiz will not be accepted. You may take as much time as you wish, provided you turn in your quiz via LEO by 11:59 pm EDT on Sunday, September 10. 1. (10 points) True or False. Justify your answers for full credit. (a) If all observations are identical in a data set, then the variance from this data set is zero. (b) There may be more than one mode in a data set. (c) Suppose the minimum for a data set is 12. A careless assistant records it as 1.2, which is the only mistake in the record keeping. Based on this piece of information alone, we are not sure if this mistake will change the median of the data set. (d) The length of the running track in a high school is 400 m. The value 400 is from a discrete data set. (e) Variance of a data set cannot be negative, but the standard deviation can be negative. (For Questions 2 to 8) Choose the correct answer. Justify your answers for full credit. (2 points each) 2. A STAT 200 instructor is interested in the average weekly study time for UMUC STAT 200 students. She teaches two sections in Fall OL1, and randomly chooses 15 students from the first section and 18 students from the second section. This sampling method is called a. cluster b. convenience c. stratified d. systematic 3. Mimi is doing a research about commute time. She plans on collecting the commute time information from her STAT 200 classmates. This sampling method is called a. cluster b. convenience c. stratified d. systematic 4. Which of the following is a qualitative variable? a. Weight in kilograms b. Number of days without precipitation c. Ethnicity d. Average daily temperature 5. 10 street lights in the UMUC Largo Academic Center were randomly selected. The average lifetime of these 10 street lights is 7500 hours. The value 7500 is a. a parameter, b. a statistic, c. neither of the above. 6. Identify the scale of measurement for the following military hierarchy: Lieutenant, Captain, Major: a. Interval b. Nominal c. Ratio d. Ordinal 7. In a histogram, frequencies are represented by_______ a. Lines b. Bars c. portions of the pie d. leaves 8. For the following boxplot of test scores, which score band has most students? (a) 45 and 60 (b) 60 and 75 (c) 85 and 100 (d) cannot be determined -------------------------------------------------------------------------------------------------------------------(For Questions 9 through 12) The checkout times (in minutes) for 10 randomly selected customers at a large supermarket during the store's busiest time on a Sunday afternoon are as follows: 6 13 8 10 5 8 13 7 8 11 9. (5 points) (Show work) Find the minimum, maximum, median, mode and mean of the checkout time. (Round the answers to two decimal places) 10. (5 points) (Show work) Prepare a frequency distribution with a class width of 2 minutes by completing the following table. Checkout Time Frequency Cumulative Relative Frequency 5.0 - 6.9 7.0 - 8.9 9.0 - 10.9 11.0 - 12.9 13.0 - 14.9 11. (2 pts) (Show work) What percentage of the checkout times was less than 9 minutes? __________________________________________________________________ 12. (4 pts) (Show work) What is the standard deviation of the checkout time in the sample? Show your intermediate calculation in the following table; you may not need all columns based on the formula you use. (Round the answer to two decimal places) Checkout Time x 6 8 5 13 8 13 10 8 7 11 x2 x-mean (x-mean)2 Sum