Exam 7: Sampling Distributions and Sampling

TABLE 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 Table 7-4, 90% of the samples will have more than what percentage of customers who will make a purchase after visiting the web site?

A study at a college in the west coast 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.

TABLE 7-2 The mean selling price of new homes in a city 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 7-2, what is the probability that the sample mean selling price was between $113,000 and $117,000?

TABLE 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 Table 7-4, what proportion of the samples will have less than 15% of customers who will make a purchase after visiting the web site?

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

If the population distribution is symmetric, the sampling distribution of the mean can be approximated by the normal distribution if the samples contain 15 observations.

TABLE 7-6 According to an article, 19% of the entire U.S. population have high-speed access to the Internet. Random samples of size 200 are selected from the U.S. population. -Referring to Table 7-6, among all the random samples of size 200, _____ % will have between 9% and 29% who have high-speed access to the Internet.

The question "How many times have you abused your spouse in the last 6 months?" will most likely result in nonresponse error.

TABLE 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 Table 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 probability that the sample mean will be between 77 and 89 minutes is_____ .

The amount of pyridoxine (in grams) per multiple vitamin is normally distributed with µ = 110 grams and ? = 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?

TABLE 7-7 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 7-7, the population mean of all possible sample proportions 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 probability that the sample mean will be greater than 88 minutes is _____ .

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

The amount of time it takes to complete an examination has a skewed-left 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 Central Limit Theorem is important in statistics because

The mean of the sampling distribution of a sample proportion is the population proportion, ?.

Which of the following types of samples can you use if you want to make valid statistical inferences from a sample to a population?

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

The standard error of the population proportion will become larger