Exam 7: Sampling Distributions

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 9% and 29% who have high-speed access to the Internet.

True or False: As the size of the sample is increased,the standard deviation of the sampling distribution of the sample mean for a normally distributed population will stay the same.

Sales prices of baseball cards from the 1960s are known to possess a right skewed distribution with a mean sale price of $5.25 and a standard deviation of $2.80.Suppose a random sample of 100 cards from the 1960s is selected.Describe the sampling distribution for the sample mean sale price of the selected cards.

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,the standard error of all possible sample proportions is ________.

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.What percentage of samples of 4 fish will have sample means between 3.0 and 4.0 pounds?

True or False: Suppose μ = 80 and σ = 20 for a population.In a sample where n = 100 is randomly taken,95% of all possible sample means will fall above 76.71.

True or False: The standard deviation of the sampling distribution of a sample proportion is where π is the population proportion.

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,the population mean of all possible sample proportions 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 between 0.99 and 1.01 centimeters?

True or False: For distributions such as the normal distribution,the arithmetic mean is considered more stable from sample to sample than other measures of central tendency.

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 7-6,95% of the samples proportions symmetrically around the population proportion will have between ________% and ________% of the customers who take advantage of online customer service.

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 200,90% will have less than ________% who have high-speed access to the Internet.

The distribution of the number of loaves of bread sold per week by a large bakery over the past 5 years has a mean of 7,750 and a standard deviation of 145 loaves.Suppose a random sample of n = 40 weeks has been selected.What is the approximate probability that the mean number of loaves sold in the sampled weeks exceeds 7,895 loaves?

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. -True or False: Referring to Table 7-4,the requirements for using a normal distribution to approximate a binomial distribution is fulfilled.

True or False: An unbiased estimator will have a value,on average across samples,equal to the population parameter value.

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 a random sample size of 75 is selected,the probability is ________ that more than half of the students in the sample will be minority students.

TABLE 7-2 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 7-2,what is the probability that the sample mean selling price was between $114,000 and $116,000?

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,the standard deviation of all the sample proportions of customers who will make a purchase after visiting the website is ________.

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.

For sample sizes greater than 30,the sampling distribution of the mean will be approximately normally distributed