# STAT 200 Introduction to Statistics - Final Examination

STAT 200 Introduction to Statistics - Final Examination

1. True or False. Justify for full credit. (25 pts) (a) If the variance from a data set is zero, then all the observations in this data set must be identical. (b) P(A AND Ac ) 1, where Ac is the complement of A. (c) The mean is always equal to the median for a normal distribution. (d) A 99% confidence interval is wider than a 95% confidence interval of the same parameter. (e) It is easier to reject the null hypothesis if we use a smaller significance level a. Refer to the following frequency distribution for Questions 2, 3, 4, and 5. Show all work. Just the answer, without supporting work, will receive no credit. A random sample of 25 customers was chosen in UMUC MiniMart between 3:00 and 4:00 PM on a Friday afternoon. The frequency distribution below shows the distribution for checkout time (in minutes). Checkout Time (in minutes) Frequency Relative Frequency 1.0 - 1.9 4 2.0 - 2.9 0.4 3.0 - 3.9 4.0 - 4.9 5 Total 25 2. Complete the frequency table with frequency and relative frequency. (5 pts) 3. What percentage of the checkout times was at least 3 minutes? (5 pts) 4. In what class interval must the median lie? Explain your answer. (5 pts) 5. Assume that the largest observation in this dataset is 4.8. Suppose this observation were incorrectly recorded as 8.4 instead of 4.8. Will the mean increase, decrease, or remain the same? Will the median increase, decrease or remain the same? Why? (5 pts) Refer to the following information for Questions 6, 7, and 8. Show all work. Just the answer, without supporting work, will receive no credit. A 6-faced die is rolled two times. Let A be the event that the outcome of the first roll is an even number, and B be the event that the outcome of second roll is greater than 4. 6. How many outcomes are there in the sample space? (5 pts) 7. What is the probability that the outcome of the second roll is greater than 4, given that the first roll is an even number? (10 pts)