Exam 7: Sampling Distributions

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 standard error for the sample mean?

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 greater than 100 grams?

The average score of all pro-golfers for a particular course has a mean of 70 and a standard deviation of 3.0.Suppose 36 pro-golfers played the course today.Find the probability that the average score of the 36 pro-golfers exceeded 71.

True or False: A sample size of 25 provides a sample variance of 400.The standard error,in this case equal to 4,is best described as the estimate of the standard deviation of means calculated from sample sizes of 25.

True or False: As the sample size increases,the effect of an extreme value on the sample mean becomes smaller.

True or False: A sampling distribution is defined as the probability distribution of possible sample sizes that can be observed from a given population.

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 less than 36.03 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.Above what value do 2.5% of the sample means fall?

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 25 fish yields a mean of 3.6 pounds,what is the Z-score for this observation?

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 exceeds the population mean by more than 2 hours?

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 was no more than $3.0 million.

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,the standard error of all the 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.If a sample of 64 fish yields a mean of 3.4 pounds,what is probability of obtaining a sample mean this large or larger?

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.What was the standard error for the sample mean salary?

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.

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 less than 37.5% who take advantage of online customer service.

Which of the following is true regarding the sampling distribution of the mean for a large sample size?

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,what is the probability that a random sample of 50 will have at least 30% of customers who will make a purchase after visiting the website?

If the expected value of a sample statistic is equal to the parameter it is estimating,then we call that sample statistic

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 between 30% and 50% of the students in the sample will be minority students.