Exam 7: Sampling Distributions

Instruction 7-5 The manager of the customer service division of a major consumer electronics company is interested in determining whether the customers who have purchased a DVD player made by the company over the past 12 months are satisfied with their products. -Referring to Instruction 7-5,if a customer survey questionnaire is included in all the DVD players made and sold by the company over the past 12 months,this method of collecting data will most likely suffer from

If the population distribution is unknown,in most cases the sampling distribution of the mean can be approximated by the normal distribution if the samples contain at least 30 observations.

Suppose the ages of students in first-year Statistics 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 statements about the sampling distribution of the sample mean age is incorrect?

________ results from the exclusion of certain groups of subjects from a population frame.

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.

The amount of pyridoxine (in grams)per multiple vitamin is normally distributed with μ = 110 grams and σ= 25 grams.A sample of 25 vitamins is to be selected.So,95% of all sample means will be greater than how many grams?

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 mean of 1080.

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.

A sample of 300 subscribers to a particular magazine is selected from a population frame of 9,000 subscribers.If,upon examining the data,it is determined that no subscriber had been selected in the sample more than once,

The sampling distribution of a sample statistic represents what would result if all possible samples from a population were drawn.

A sample is always a good representation of the target population.

Instruction 7-3 The lifetimes of a certain brand of light bulbs are known to be normally distributed with a mean of 1,600 hours and a standard deviation of 400 hours.A random sample of 64 of these light bulbs is taken. -Referring to Instruction 7-3,the probability is 0.20 that the sample mean lifetime differs from the population mean lifetime by at least how many hours?

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.

At a computer manufacturing company,the actual size of computer chips is normally distributed with a mean of 1 cm and a standard deviation of 0.1 cm.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 cm?

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.So,95% of the sample means based on samples of size 36 will be between ________ and ________.

Instruction 7-3 The lifetimes of a certain brand of light bulbs are known to be normally distributed with a mean of 1,600 hours and a standard deviation of 400 hours.A random sample of 64 of these light bulbs is taken. -The mean of the sampling distribution of a sample proportion is the population proportion,π.

The amount of pyridoxine (in grams)per multiple vitamin is normally distributed with μ = 110 grams and σ= 25 grams.A sample of 25 vitamins is to be selected.So,the middle 70% of all sample means will fall between what two values?

Sampling error can be completely eliminated by taking larger sample sizes.

Systematic samples are less efficient than stratified sample.

The standard error of the mean is also known as the standard deviation of the sampling distribution of the sample mean.