Exam 7: Sampling and Sampling Distributions

The question: "Have you used any form of illicit drugs over the past 2 months?" will most likely result in measurement error if the question is answered.

TABLE 7-2 The time spent studying by students in the week before final exams follows a normal distribution with a standard deviation of 8 hours.A random sample of 4 students was taken in order to estimate the mean study time for the population of all students. -Referring to Table 7-2,what is the probability that the sample mean differs from the population mean by less than 2 hours?

Which of the following is true regarding the sampling distribution of the mean for a large sample size?

TABLE 7-4 The lifetimes of a certain brand of light bulbs are known to be normally distributed with a mean of 1,600 hours and a standard deviation of 400 hours.A random sample of 64 of these light bulbs is taken. -Referring to Table 7-4,the probability is 0.15 that the sample mean lifetime is more than how many hours?

Which of the following is not a reason for selecting a sample?

Suppose μ = 50 and σ = 10 for a population.In a sample where n = 100 is randomly taken,95% of all possible sample means will fall between 48.04 and 51.96.

Using different frames to generate data can lead to totally different conclusions.

TABLE 7-7 Online customer service is a key element to successful online retailing.According to a marketing survey,37.5% of online customers take advantage of the online customer service.Random samples of 200 customers are selected. -Referring to Table 7-7,90% of the samples proportions symmetrically around the population proportion will have between ________ % and ________ % of the customers who take advantage of online customer service.

A convenience sample is a type of probability sample.

Major league baseball salaries averaged $3.26 million with a standard deviation of $1.2 million in a recent year.Suppose a sample of 100 major league players was taken.Find the approximate probability that the mean salary of the 100 players exceeded $4.0 million.

If the amount of gasoline purchased per car at a large service station has a population mean of 15 gallons and a population standard deviation of 4 gallons and a random sample of 4 cars is selected,there is approximately a 68.26% chance that the sample mean will be between 13 and 17 gallons.

TABLE 7-1 The manager of the customer service division of a major consumer electronics company is interested in determining whether the customers who have purchased a DVD player made by the company over the past 12 months are satisfied with their products. -Referring to Table 7-1,if there are 4 different brands of DVD players made by the company,the best sampling strategy would be to use a

The standard error of the population proportion will become larger

Which of the following is not a reason for the need for sampling?

TABLE 7-3 The mean selling price of new homes in a small town over a year was $115,000.The population standard deviation was $25,000.A random sample of 100 new home sales from this city was taken. -Referring to Table 7-3,what is the probability that the sample mean selling price was between $113,000 and $117,000?

TABLE 7-1 The manager of the customer service division of a major consumer electronics company is interested in determining whether the customers who have purchased a DVD player made by the company over the past 12 months are satisfied with their products. -Referring to Table 7-1,which of the following questions in the survey will not likely induce a measurement error?

TABLE 7-5 According to a survey,only 15% of customers who visited the website of a major retail store made a purchase.Random samples of size 50 are selected. -A study at a college in the west coast reveals that,historically,45% of the students are minority students.If random samples of size 75 are selected,80% of the samples will have less than ________ % of minority students.

TABLE 7-5 According to a survey,only 15% of customers who visited the website of a major retail store made a purchase.Random samples of size 50 are selected. -A study at a college in the west coast reveals that,historically,45% of the students are minority students.If random samples of size 75 are selected,the standard error of the proportion of students in the samples who are minority students is ________.

At a computer manufacturing company,the actual size of computer chips is normally distributed with a mean of 1 centimeter and a standard deviation of 0.1 centimeter.A random sample of 12 computer chips is taken.What is the probability that the sample mean will be below 0.95 centimeters?

The fact that the sample means are less variable than the population data can be observed from the standard error of the mean.