Exam 7: Sampling and Sampling Distributions

Which of the following is true about statistics such as the sample mean or sample proportion?

A local company makes snack size bags of potato chips.The company produces batches of 400 snack size bags using a process designed to fill each bag with an average of 2 ounces of potato chips.However,due to imperfect technology,the actual amount placed in a given bag varies.Assume the population of filling weights is normally distributed with a standard deviation of 0.1 ounces.The company periodically weighs samples of 10 bags to ensure the proper filling process.The last five sample means,in ounces,were 1.99,2.02,2.07,1.96,and 2.01.Is the production process under control?

A random sample of size 36 is taken from a population with mean and standard deviation . Refer to Exhibit 7-5.The probability that the sample mean is less than 15 is ________.

Over the entire six years that students attend an Ohio elementary school,they are absent,on average,28 days due to influenza.Assume that the standard deviation over this time period is days.Upon graduation from elementary school,a random sample of 36 students is taken and asked how many days of school they missed due to influenza. Refer to Exhibit 7-1.What is the expected value for the sampling distribution of the number of school days missed due to influenza?

For any sample size n,the sampling distribution of is normal if the population from which the sample is drawn is uniformly distributed.

Suppose 35% of homes in a Miami,Florida,neighborhood are under water (in other words,the amount due on the mortgage is larger than the value of the home).There are 160 homes in the neighborhood and 30 of those homes are owned by your friends.What is the probability that less than 30% of your friend's homes are under water?

In a recent investigation,the National Highway Traffic Safety Administration (NHTSA)found that the Chevrolet Volt and other electric vehicles do not pose a greater risk of fire than gasoline-powered vehicles (The Boston Globe,January 25,2012).Specifically,it was determined that "no discernible defect trend exists." Suppose a consumer advocacy group wants to verify some of these claims by constructing a

Susan has been on a bowling team for 14 years.After examining all of her scores over that period of time,she finds that they follow a normal distribution.Her average score is 225,with a standard deviation of 13. Refer to Exhibit 7-3.If during a typical week Susan bowls 16 games,what is the probability that her average score is more than 230?

Nonresponse bias occurs when those responding to a survey or poll differ systematically from the non-respondents.

The labor force participation rate is the number of people in the labor force divided by the number of people in the country that are of working age and not institutionalized.The BLS reported in February of 2012 that the labor force participation rate in the United States was 63.7% (Calculatedrisk.com).A marketing company asks 120 working-age people if they either have a job or are looking for a job,or,in other words,whether they are in the labor force. Refer to Exhibit 7-8.What is the probability that less than 60% of those surveyed are members of the labor force?