Exam 7: Sampling and Sampling Distributions

TABLE 7-5 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 Table 7-5, the requirements for using a normal distribution to approximate a binomial distribution is fulfilled.

Suppose μ = 50 and σ = 10 for a population. In a sample where n = 100 is randomly taken, 90% of all possible sample means will fall between 49 and 51.

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

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?

A manufacturer of power tools claims that the mean 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 mean of the sampling distribution of the sample mean is ________ minutes.

Suppose μ= 80 and σ = 20 for a population. In a sample where n = 100 is randomly taken, 95% of all possible sample means will fall above 76.71.

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.

Measurement error will become an ethical issue when the findings are presented without reference to sample size and margin of error.

TABLE 7-1 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 Table 7-1, which of the following questions in the survey will NOT likely induce a measurement error?

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?

TABLE 7-6 According to an article, 19% of the entire population in a developing country have high-speed access to the Internet. Random samples of size 200 are selected from the country's population. -Referring to Table 7-6, among all the random samples of size 200, 90% will have less than ________% who have high-speed access to the Internet.

You stand at the main entrance to a department store and pick the first 20 customers that enter the store after it has opened its door for business on a single day. This is an example of a systematic sample.

TABLE 7-2 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 7-2, what is the probability that the sample mean differs from the population mean by more than 3 hours?

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

Using different frames to generate data can lead to totally different conclusions.

A manufacturer of power tools claims that the mean 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 greater than 88 minutes is ________.

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. Which of the following will be a good frame for drawing a sample?

TABLE 7-3 The mean selling price of new homes in a small town over a year was $115,000. The population standard deviation was $25,000. A random sample of 100 new home sales from this city was taken. -Referring to Table 7-3, what is the probability that the sample mean selling price was more than $110,000?

The amount of time it takes to complete an examination has a left-skewed distribution with a mean of 65 minutes and a standard deviation of 8 minutes. If 64 students were randomly sampled, the probability that the sample mean of the sampled students exceeds 71 minutes is approximately 0.

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 will be approximately normal only if the population sampled is normal.