Exam 7: Sampling and Sampling Distributions

The amount of bleach a machine pours into bottles has a mean of 36 oz. with a standard deviation of 0.15 oz. Suppose we take a random sample of 36 bottles filled by this machine. The probability that the mean of the sample is between 35.95 and 35.98 oz. is ________.

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 more than 3 hours?

Sampling error can be reduced by taking larger sample sizes.

If the population distribution is symmetric, the sampling distribution of the mean can be approximated by the normal distribution if the samples contain 15 observations.

Assume that house prices in a neighborhood are normally distributed with a standard deviation of $20,000. A random sample of 16 observations is taken. What is the probability that the sample mean differs from the population mean by more than $5,000?

Coverage error results in a ________.

The professor of a business statistics class wanted to find out the mean amount of time per week her students spent studying for the class. She divided the fifty students on her roster into ten groups starting from the first student on the roster. The first student was randomly selected from the first group. Then every tenth student was selected from the remaining students. This is an example of a cluster sample.

The amount of tea leaves in a can from a particular production line is normally distributed with μ = 110 grams and σ = 25 grams. A sample of 25 cans is to be selected. What is the probability that the sample mean will be less than 100 grams?

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 7-1 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, the manager decides to ask a sample of customers, who have bought a DVD player made by the company and filed a complaint over the past year, to fill in a survey about whether they are satisfied with the product. This method will most likely suffer from

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

Selection bias occurs more frequently in systematic samples than in simple random samples.

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, 95% of the samples will have more than ________ % of minority students.

To obtain a sample of 10 books in the store, the manager walked to the first shelf next to the cash register to pick the first 10 books on that shelf. This is an example of a

Measurement error will become an ethical issue when the findings are presented without reference to sample size and margin of error.

TABLE 7-6 According to an article, 19% of the entire population in a developing country have high-speed access to the Internet. Random samples of size 200 are selected from the country's population. -Referring to Table 7-6, among all the random samples of size 200, ________ % will have less than 20% who have high-speed access to the Internet.

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, ________ % of the samples are likely to have between 35% and 40% who take advantage of online customer service.

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, then 99.73% of all cars will purchase between 3 and 27 gallons.

Which of the following sampling methods will more likely be susceptible to ethical violation when used to form conclusions about the entire population?

There can be only one sample selected from a population.