Exam 7: Sampling and Sampling Distributions

TABLE 7-4 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 Table 7-4,what is the probability that the sample mean lifetime is more than 1,550 hours?

Which of the following scenarios will yield a nonprobability sample?

Which of the following sampling methods is a probability sample?

The question: "How much did you earn last year rounded to the nearest hundreds of dollars?" will most likely result in measurement error.

A population frame for a survey contains a listing of 72,345 names.Using a table of random numbers,how many digits will the code numbers for each member of your population contain?

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

TABLE 7-5 According to a survey,only 15% of customers who visited the website of a major retail store made a purchase.Random samples of size 50 are selected. -Referring to Table 7-5,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?

Sampling error becomes an ethical issue if the findings are purposely presented without reference to sample size and margin of error so that the sponsor can promote a viewpoint that might otherwise be truly insignificant.

The Dean of Students mailed a survey to a total of 400 students.The sample included 100 students randomly selected from each of the freshman,sophomore,junior,and senior classes on campus last term.What sampling method was used?

The sample proportion is an unbiased estimate of the population proportion.

The distribution of the number of loaves of bread sold per day by a large bakery over the past 5 years has a mean of 7,750 and a standard deviation of 145 loaves.Suppose a random sample of n = 40 days has been selected.What is the approximate probability that the mean number of loaves sold in the sampled days exceeds 7,895 loaves?

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

The Central Limit Theorem ensures that the sampling distribution of the sample mean approaches a normal distribution as the sample size increases.

A telemarketer set the company's computerized dialing system to contact every 25th person listed in the local telephone directory.What sampling method was used?

Which of the following sampling methods will more likely be susceptible to ethical violation when used to form conclusions about the entire 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 sampling distribution of the sample mean has a standard error of 0.15.

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.90% of the sample means will be greater than what value?

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 less than 100 grams?

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?

To demonstrate a sampling method,the instructor in a class picked the first 5 students sitting in the last row of the class.This is an example of a