Sheet 1

 School of Business, Business, Economics & Political   Science   Statistics, (15BBST20P) (15BBST20P) Prep. Year-2015/2016  Sheet 1& Model Answer  Answer  Chapter 1 1.1 A politician who is running for the office o f mayor of a city with 25,000 registered voters commissions a survey. In the survey, 48% of th e 200 registered voters interviewed say they plan to vote for her.

a. What is the population of interest?  b. What is the sample? c. Is the value 48% a parameter or statistic? Explain. Answer:

a. The 25,000 registered voters of the city.  b. 200 interviewed registered voters. c. It’s a statistic, because it was calculated from a sample (200 voters).

1.2 A manufacturer of computer chips claims that less than 10% of his products are defective. When 1,000 chips were drawn from a large production, 7.5% were found to be defective.

a. What is the population of interest?  b. What is the sample? c. What is the parameter? d. What is the statistic?

e. Does the value 10% refer to the parameter or to the statistic? f.

Is the value 7.5% a parameter or a statistic?

g. Explain briefly how the statistic can be used to make inferences about the  parameter to test the claim. Answer:

a.  b. c. d. e. f. g.

All production of computer chips. The 1000 drawn chips from the production. Percentage of defective computer chips. 7.5%. Parameter. Statistic. Because the percentage of defective computer chips calculated from the sample is 7.5%, i.e. less than 10%, we can conclude with a certain level of confidence that the manufacturer’s claim is true.

1.3 A company has developed a new computer sound card whose average lifetime is unknown. In order to estimate this average, 200 sound cards are randomly selected from a large product ion line and tested; their average lifetime is found to be 5 years.

a. What is the population of interest?  b. What is the sample? c. What is the parameter? d. What is the value of the respective statistic? Answer:

a.  b. c. d.

All new computer sound cards. The 200 randomly selected sound cards. The unknown average life time for new sound cards. 5 years average life time.

1.4 In the following multiple-choice questions, circle the correct answer: •

The process of using sample statistics to draw conclusions about population parameters is called:

a. finding the significance level.  b. calculating descriptive statistics.

c. doing inferential statistics.

d. calculating the confidence level. •

A study is under way to determine the average height of all 32,000 adult pine trees in a certain national forest. The heights of 500 randomly selected adult pine trees are measured and analyzed. The sample in this study is:

a. the average height of the 500 randomly selected adult pine trees.  b. the average height of all the adult pine trees in this forest. c. all the adult pine trees in this forest. d. the 500 adult pine trees selected at random from this forest.