Exam 7: Sampling Distributions

Instruction 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 Instruction 7.4,the average of all the sample proportions of customers who will make a purchase after visiting the web site is_________ .

A manufacturer of power tools claims that the average amount of time required to assemble their top-of-the-line table saw is 80 minutes with a standard deviation of 40 minutes. -Suppose a random sample of 64 purchasers of this table saw is taken.The standard deviation of the sampling distribution of the sample mean is ________minutes.

Instruction 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 Instruction 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 time required for an oil and filter change on a car 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 would you expect the standard error of the mean to be?

The amount of bleach a machine pours into bottles has a mean of 1080 grams with a standard deviation of 4.5 grams.Suppose we take a random sample of 36 bottles filled by this machine -The probability that the mean of the sample is between 1018.9 and 1022.3 grams is _____.

For air travellers,one of the biggest complaints is of the waiting time between when the aeroplane taxis away from the terminal until the flight takes off.This waiting time is known to have a skewed-right 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 aeroplane taxis away from the terminal until the flight takes off for these 100 flights.

Sampling distributions describe the probability distribution of

Instruction 7.1 Times spent studying by students in the week before final exams follow 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 Instruction 7.1,what is the probability that the sample mean differs from the population mean by more than 3 hours?

A manufacturer of power tools claims that the average amount of time required to assemble their top-of-the-line table saw is 80 minutes with a standard deviation of 40 minutes. -Suppose a random sample of 64 purchasers of this table saw is taken.The probability that the sample mean will be between 77 and 89 minutes is________

Instruction 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 Instruction 7.4,the requirements for using a normal distribution to approximate a binomial distribution is fulfilled.

A sample of size 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 samples of size 25.

Instruction 7.1 Times spent studying by students in the week before final exams follow 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 Instruction 7.1,what is the probability that the sample mean exceeds the population mean by more than 2 hours?

If the amount of petrol purchased per car at a large petrol station has a population mean of $15 and a population standard deviation of $4,then 99.73% of all cars will purchase between $3 and $27.

Instruction 7.5 According to an article, 19% of the entire Australian population have high-speed access to the Internet. Random samples of size 200 are selected from the Australian population. -Referring to Instruction 7.5,among all the random samples of size 200,_________ % will have less than 20% who have high-speed access to the Internet.

The amount of bleach a machine pours into bottles has a mean of 1080 grams with a standard deviation of 4.5 grams.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 4.5.

A study at a university in New South Wales reveals that,historically,45% of their students are minority students.If random samples of size 75 are selected,95% of the samples will have more than _________ % of minority students.

The Central Limit Theorem is considered powerful in statistics because it works for any population distribution provided the sample size is sufficiently large and the population mean and standard deviation are known.

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.

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

Suppose the ages of students in first-year Statistics 101 follow a skewed-right distribution with a mean of 23 years and a standard deviation of 3 years.If we randomly sampled 100 students,which of the following is true about the sampling distribution of the sample mean?