Exam 7: Sampling Distributions

Suppose a sample of n = 50 items is selected from a population of manufactured products and the weight,X,of each item is recorded.Prior experience has shown that the weight has a probability distribution with μ= 6 ounces and σ = 2.5 ounces.Which of the following is true about the sampling distribution of the sample mean if a sample size of 15 is selected?

Which of the following statements about the sampling distribution of the sample mean is incorrect?

TABLE 7-4 According to a survey,only 15% of customers who visited the website of a major retail store made a purchase.Random sample sizes of 50 are selected. -A study at a college in the west coast reveals that,historically,45% of the students are minority students.The expected percentage of minority students in their next group of freshmen is ________.

TABLE 7-5 According to an article,19% of the entire population in a developing country has high-speed access to the Internet.Random sample sizes of 200 are selected from the country's population. -Referring to Table 7-5,among all the random sample sizes of 200,________% will have between 14% and 24% who have high-speed access to the Internet.

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 35.94 and 36.06 oz.is ________.

The amount of time required for an oil and filter change on an automobile is normally distributed with a mean of 45 minutes and a standard deviation of 10 minutes.A random sample of 16 cars is selected.What is the probability that the sample mean will be between 39 and 48 minutes?

TABLE 7-1 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 7-1,what is the probability that the sample mean differs from the population mean by more than 3 hours?

+The amount of time required for an oil and filter change on an automobile is normally distributed with a mean of 45 minutes and a standard deviation of 10 minutes.A random sample of 16 cars is selected.What is the standard error of the mean?

A sample that does not provide a good representation of the population from which it was collected is referred to as a(n)________ sample.

True or False: 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 64 cars is selected,there is approximately a 95.44% chance that the sample mean will be between 14 and 16 gallons.

TABLE 7-6 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 7-6,________% of the samples are likely to have between 35% and 40% who take advantage of online customer service.

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?

True or False: The standard error of the sampling distribution of a sample proportion is where p is the sample proportion.

The standard error of the mean for a sample of 100 is 30.In order to cut the standard error of the mean to 15,we would

The owner of a fish market has an assistant who has determined that the weights of catfish are normally distributed,with a mean of 3.2 pounds and a standard deviation of 0.8 pound.If a sample of 16 fish is taken,what would the standard error of the mean weight equal?

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 between 100 and 120 grams?

TABLE 7-4 According to a survey,only 15% of customers who visited the website of a major retail store made a purchase.Random sample sizes of 50 are selected. -Referring to Table 7-4,90% of the samples will have more than what percentage of customers who will make a purchase after visiting the website?

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 ________.

Why is the Central Limit Theorem so important to the study of sampling distributions?

TABLE 7-4 According to a survey,only 15% of customers who visited the website of a major retail store made a purchase.Random sample sizes of 50 are selected. -A study at a college in the west coast reveals that,historically,45% of the students are minority students.If random sample sizes of 75 are selected,95% of the samples will have more than ________% of minority students.