Exam 7: Sampling Distributions

Suppose ? = 80 and $\sigma$ = 20 for a population.In a sample where n = 100 is randomly taken,95% of all possible sample means will fall above 76.08.

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 sampling distribution of the sample mean has a standard error of 0.15.

SCENARIO 7-5 According to an article,19% of the entire population in a developing country has high-speed access to the Internet.Random samples of size 200 are selected from the country's population. -Referring to Scenario 7-5,among all the random samples of size 200,90 % will have less than _____ % that has high-speed access to the Internet.

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?

As the sample size increases,the standard error of the mean increases.

For air travelers,one of the biggest complaints is of the waiting time between when the airplane taxis away from the terminal until the flight takes off.This waiting time is known to have a right skewed distribution with a mean of 10 minutes and a standard deviation of 8 minutes.Suppose 100 flights have been randomly sampled.Describe the sampling distribution of the mean waiting time between when the airplane taxis away from the terminal until the flight takes off for these 100 flights.

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 is between 45 and 52 minutes?

SCENARIO 7-5 According to an article,19% of the entire population in a developing country has high-speed access to the Internet.Random samples of size 200 are selected from the country's population. -Referring to Scenario 7-5,among all the random samples of size 200,_____% will have more than 30% 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 sampling distribution of the sample mean will be approximately normal only if the population sampled is normal.

A sampling distribution is a distribution for a statistic.

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

SCENARIO 7-4 According to a survey,only 15% of customers who visited the web site of a major retail store made a purchase.Random samples of size 50 are selected. -Referring to Scenario 7-4,the requirements for using a normal distribution to approximate a binomial distribution is fulfilled.

SCENARIO 7-4 According to a survey,only 15% of customers who visited the web site of a major retail store made a purchase.Random samples of size 50 are selected. -Referring to Scenario 7-4,90% of the samples will have less than what percentage of customers who will make a purchase after visiting the web site?

The owner of a fish market has an assistant who has determined that the weights of catfish are normally distributed,with mean of 3.2 pounds and standard deviation of 0.8 pound.If a sample of 25 fish yields a mean of 3.6 pounds,what is the Z-score for this observation?

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.

SCENARIO 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 Scenario 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.

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 .

To use the normal distribution to approximate the binomial distribution,we need _____ and _____ to be at least 5.

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.So,the middle 95% of the sample means based on samples of size 36 will be between _____ and_____ .

For sample size 1,the sampling distribution of the mean will be normally distributed