Practice Assignment (to be discussed randomly, Wednesday, Jan. 27).

1) In a survey of 2,500 bikers at the 1993 Laconia Motorcycle Rally, 98 percent of respondents said they opposed laws requiring the use of motorcycle helmets.

(a) Do you think that 98% is a good estimate for the fraction of bikers who oppose helmet laws? If not, in what direction do you think the estimate will be off?

(b) Do you think that 98% is a good estimate for the fraction of bikers at the Laconia rally who oppose helmet laws? If not, in what direction do you think the estimate will be off?

(c) Outline the design of a study you could use to estimate the proportion of motorcycle riders who oppose such a law?

2) Different types of writing can sometimes be distinguished by the lengths of the words used. A student interested in this fact wants to study the lengths of words used by Tom Wolfe in his novels. She picks a Wolfe novel at random, randomly selects 250 pages, and then closes her eyes and points to a spot on each page, recording the length of the word under her finger.

(a) What is the population in this study?

(b) What is the sample?

(c) What is the variable measured?

(d) Do you think this method will give a representative sample?

3) (p. 237) 3.8

Also identify the response and explanatory variables.

Homework Assignment (Due Friday, Jan. 29)

1) A study was conducted to estimate the average length of a prison sentence for prisoners at a correctional facility. A random sample of current prisoners was obtained on a particular day, and they were monitored to the completion of their sentence. The information from this sample was used to estimate the average length of a prison sentence.

(a) Identify the population in this study

(b) Identify the sample in this study

(c) What is the variable of interest that is being measured?

(d) Do you think this method will give a representative sample? Explain.

2) (p. 236) 3.4, Also identify the experimental units or subjects.

3) (p. 251) 3.14, Give lots of detail for your procedure in (b). Your final answer should list the names of all the subjects, with clear explanation of how they were obtained.

4) (p. 255) 3.30

5) A company employs 1000 males and 200 females. A management task force officer polls a stratified random sample of 100 males and 20 females.

(a) What is the chance that a particular female employee will be polled?

(b) What is the chance that a particular male employee will be polled?

(c) Does this sample meet the requirements of a simple random sample? Explain carefully.

6) The college president wants to take a survey of 1,500 students in the school. Each student has an identification number on the administrative computer. Identify the following methods as simple random sampling, convenience sampling, stratified random sampling, systematic sampling, or cluster sampling.

(a) Students are listed alphabetically and then this list is broken into 50 sections, 30 students each. The administration selected a random number between 01 and 30, obtaining 23. Then they selected the 23rd student from each of the 50 sections.

(b) The school groups the students by class rank: freshmen, sophomores, juniors, seniors. The computer's random number generator is used to select 25 identification numbers form each of the 4 class-rank lists. Students corresponding to those selected identification numbers are interviewed.

(c) The school constructs a list of the undergraduate majors and takes a simple random sample of 6 majors, interviewing all the students in those 6 majors.

(d) For each method, can you identify how many freshmen will be in the sample? Explain.