Estimation of Population

The scores of a random sample of 100 high school students on a standardized mathematics test in school A gave a mean of 78 and a standard deviation of 20. Find the 95% confidence interval estimate for the true average score in mathematics in this standardized test.

• 1.96 to 3.92

• 76 to 80

• 74.08 to 81.92

• 74.80 to 81.29

A point estimate of a population consists of how many numbers?

• 1

• 2

• 10

• infinite

What is a point estimate?

• average of sample values

• average of population values

• a single value that represents the unknown sample statistic

• a single value that represents the unknown population parameter

A sample of 600 ninth graders was selected at random and asked how much time they spend on homework each day. Of the ninth graders selected, 220 spend less than 2 hours on homework each day. If the conclusion was drawn that “approximately 1.35 million ninth graders spend less than 2 hours on homework each day,” which of the following is closest to the population, in millions, of ninth graders?

• 0.368

• 0.495

• 3.68

• 5.84

Complete the following statement about the change in size. If you increase the size of your sample, the Margin of Error will . . . .

• increase

• decrease

• stay the same

A sample of 600 ninth graders was selected at random and asked how much time they spend on homework each day. Of the ninth graders selected, 220 spend less than 2 hours on homework each day. If the conclusion was drawn that “approximately 1.35 million ninth graders spend less than 2 hours on homework each day,” which of the following is closest to the population, in millions, of ninth graders?

• 0.368

• 0.495

• 3.68

• 5.84

Margin of error equals:

• Critical Value ∗ standard Error

• z*

• 1.96

• Standard Error

A random sample of 121 bottles of cologne showed an average content of 4 ounces. It is known that the population standard deviation of the contents is 0.22 ounces. In this problem, the 4 ounces is?

• A parameter

• A statistic

• The standard error of the mean

• The average content of colognes in the long run

When a 99% confidence interval is calculated instead of a 95% confidence interval with n being the same, the maximum error of estimate will be?

• smaller

• larger

• the same

• not be determined

The scores of a random sample of 100 high school students on a standardized mathematics test in school A gave a mean of 78 and a standard deviation of 20. What is the best point estimate of the true average score in this standardized mathematics test?

• 20

• 78

• 95

• 100