Alexander College Comm 291 Assignment 3 Instructor: Alfred Kong Due date: 16th November 2016 The assignment is due at the beginning of the class. Late assignment will not be accepted. For this assignment, complete all of the following questions. Question 1 Suppose that past history shows that 60% of college students prefer Brand C cola. A sample of 15 students is to be selected. a) Explain why the probability distribution should be binomial. b) Construct the whole probability distribution for this example. c) Use the normal distribution to approximate the probability of getting less than 10 people prefer Brand C cola in the sample. How much does your answer differ than the exact probability calculated by using the binomial distribution? Question 2 The breaking strength of plastic bags used for packaging produce is normally distributed, with a mean of 5 pounds per square inch and a standard deviation of 1.5 pounds per square inch. What proportion of the bags have a breaking strength of a. less than 3.17 pounds per square inch? b. at least 3.6 pounds per square inch? c. between 5 and 5.5 pounds per square inch? Question 3 Time spent using email per session is normally distributed, with a population mean of 8 minutes and population standard deviation of 2 minutes. If you select a random sample of 25 sessions, a. what is the probability that the sample mean is between 7.8 and 8.2 minutes? b. what is the probability that the sample mean is between 7.5 and 8 minutes? c. If you select a random sample of 100 sessions, what is the probability that the sample mean is between 7.8 and 8.2 minutes? d. Explain the difference in the results of a. and c