Exam 6: Sampling and Sampling Distributions

THE NEXT QUESTIONS ARE BASED ON THE FOLLOWING INFORMATION: The following data give the number of pets owned for a population of 4 families. -Find the population mean and population standard deviation.

THE NEXT QUESTIONS ARE BASED ON THE FOLLOWING INFORMATION: Suppose you flip a coin four times.For every head,you receive one point,and for every tail,you lose one point. -What is the probability that the mean number of points you receive on four flips is 0?

The amount of time that you have to wait before seeing the doctor in the doctor's office is normally distributed with a mean of 15.2 minutes and a standard deviation of 15.2 minutes.If you take a random sample of 35 patients,what is the probability that the average wait time is greater than 20 minutes? (Hint: Round the probability value to 2 decimal places. )

THE NEXT QUESTIONS ARE BASED ON THE FOLLOWING INFORMATION: Each member of a random sample of 20 business economists was asked to predict the rate of inflation for the coming year.Assume that the predictions for the whole population of business economists follow a normal distribution with standard deviation 2%. -The probability is 0.01 that the sample standard deviation is larger than what value?

THE NEXT QUESTIONS ARE BASED ON THE FOLLOWING INFORMATION: You have recently joined a country club.Suppose that the number of times you expect to play golf in a month is represented by a normally distributed random variable with a mean of 10 and a standard deviation of 2.4. -Over the course of the next year,the probability is 85% that you average less than how many games per month?

THE NEXT QUESTIONS ARE BASED ON THE FOLLOWING INFORMATION: The mean selling price of new homes in a city over a year was $120,000.The population standard deviation was $28,000.A random sample of 100 new home sales from this city was taken. -What is the probability that the sample mean selling price was between $118,000 and $122,000?

THE NEXT QUESTIONS ARE BASED ON THE FOLLOWING INFORMATION: The number of hours spent studying by students on Michigan State campus in the week before final exams follows a normal distribution with standard deviation 9.5 hours.A random sample of these students is taken to estimate the population mean number of hours studying. -How large a sample is needed to ensure that the probability that the sample mean differs from the population mean by more than 2.1 hours is less than 0.05?

The variance of the sampling distribution of the sample mean is equal to the variance of the population mean divided by the square root of the sample size.

Suppose a friend asserted that the population distribution of selling prices of new homes in this city was almost certainly not normal.How would you respond?

If the standard error of the sampling distribution of the sample proportion is 0.0229 for samples of size 400,then the population proportion must be either:

In examining the invoices issued by a company,an auditor finds that the dollar amounts of invoices have a mean of $1,732 and a standard deviation of $298.What is the probability that for a sample of 45 invoices,the average invoice is greater than $1,800?

If all possible random samples of size n are taken from a population,and the mean of each sample is determined,the mean of the sample distribution is:

The results of a recent survey indicated that 17.7% of all U.S.adults had taken a commercial airplane flight during the last year.If we take a random sample of 200 adults,what is the probability that more than 20% flew during the past year?

THE NEXT QUESTIONS ARE BASED ON THE FOLLOWING INFORMATION: A store has determined that 28% of all refrigerators purchasers will also purchase a service agreement.In one month,250 refrigerators are sold to customers who can be regarded as a random sample of all purchasers. -Without doing the calculations,state in which of the following ranges the sample proportion is most likely to be: 0.27 to 0.29,0.28 to 0.30,0.29 to 0.31,and 0.30 to 0.32.

THE NEXT QUESTIONS ARE BASED ON THE FOLLOWING INFORMATION: It is estimated that 1.3% of all items produced on an assembly line have some form of defect.You randomly select 60 items for inspection. -An advertisement claims that four out of five doctors recommend a particular product.A consumer group wants to test that claim,and takes a random sample of 30 doctors.The consumer group finds that of this group of doctors,only 0.75 would recommend the product.What is the probability that the proportion of doctors in this sample who recommend the product is 0.75 or less? Do you have reason to doubt the manufacturer's claim? Explain.

The mean of the sampling distribution of the sample proportion ,when the sample size n = 100 and the population proportion P = 0.92,is 92.0

A basketball player shoots 60 free throws a day and historically makes 75 percent of them.What is the probability that he will make at most 80 percent tomorrow?

THE NEXT QUESTIONS ARE BASED ON THE FOLLOWING INFORMATION: It is estimated that 1.3% of all items produced on an assembly line have some form of defect.You randomly select 60 items for inspection. -What is the probability that more than 1.5% of the 60 items have some form of defect?

The larger the sample size,the larger the standard error of the sample proportion.

The central limit theorem states that if all possible random samples of size n are taken from any population,the sampling distribution of sample means becomes approximately normal when the sample size n is large enough.