Each name is randomly assigned a number. The names with numbers 1 through 1,000

b. The schools are divided into five groups according to grade level taught at the school:

K–2, 3 –5, 6 –7, 8 –9, 10 –12. Five separate sampling frames are constructed, one for each group. A simple random sample of 200 parents or guardians is selected from each group.

c. The school district is also concerned that the parent or guardian’s opinion may differ

depending on the age and sex of the student. Each name is randomly assigned a num- ber. The names with numbers 1 through 1,000 are selected for the survey. The parent is asked to fill out a separate survey for each of their currently enrolled children. 2.11 A professional society, with a membership of 45,000, is designing a study to evaluate their membership’s satisfaction with the type of sessions presented at the society’s annual meeting. In each of the following descriptions of the method of selecting participants in the survey, iden- tify the type of sampling method used simple random sampling, stratified sampling, or cluster sampling.

a. The society has an alphabetical listing of all its members. They assign a number to

each name and then using a computer software program they generate 1,250 numbers between 1 and 45,000. They select these 1,250 members for the survey.

b. The society is interested in regional differences in its membership’s opinion. Therefore,

they divide the United States into nine regions with approximately 5,000 members per region. They then randomly select 450 members from each region for inclusion in the survey.

c. The society is composed of doctors, nurses, and therapists, all working in hospitals.

There are a total of 450 distinct hospitals. The society decides to conduct onsite in-person interviews, so they randomly select 20 hospitals and interview all members working at the selected hospital. 2.12 For each of the following situations, decide what sampling method you would use. Provide an explanation of why you selected a particular method of sampling.

a. A large automotive company wants to upgrade the software on its notebook computers.

A survey of 1,500 employees will request information concerning frequently used soft- ware applications such as spreadsheets, word processing, e-mail, Internet access, statisti- cal data processing, and so on. A list of employees with their job categories is available.

b. A hospital is interested in what types of patients make use of their emergency room

facilities. It is decided to sample 10 of all patients arriving at the emergency room for the next month and record their demographic information along with type of service required, the amount of time patient waits prior to examination, and the amount of time needed for the doctor to assess the patient’s problem. 2.13 For each of the following situations, decide what sampling method you would use. Provide an explanation of why you selected a particular method of sampling.

a. The major state university in the state is attempting to lobby the state legislator for a bill

that would allow the university to charge a higher tuition rate than the other universities in the state. To provide a justification, the university plans to conduct a mail survey of its alumni to collect information concerning their current employment status. The university grants a wide variety of different degrees and wants to make sure that information is obtained about graduates from each of the degree types. A 5 sample of alumni is considered sufficient.

b. The Environmental Protection Agency EPA is required to inspect landfills in the

United States for the presence of certain types of toxic material. The materials were sealed in containers and placed in the landfills. The exact location of the containers is no longer known. The EPA wants to inspect a sample of 100 containers from the 4,000 containers know to be in the landfills to determine if leakage from the contain- ers has occurred. 2.5 Designs for Experimental Studies Engin. 2.14 Researchers ran a quality control study to evaluate the quality of plastic irrigation pipes. The study design involved a total of 24 pipes, with 12 pipes randomly selected from each of two manufacturing plants. The pipes were manufactured using one of two water temperatures and one of three types of hardeners. The compressive strength of each pipe was determined for analysis. The experimental conditions are as follows: Pipe No. Plant Temperature °F Hardener 1 1 200 H 1 2 1 175 H 2 3 2 200 H 1 4 2 175 H 2 5 1 200 H 1 6 1 175 H 2 7 2 200 H 1 8 2 175 H 2 9 1 200 H 3 10 1 175 H 3 11 2 200 H 3 12 2 175 H 3 13 1 200 H 3 14 1 175 H 3 15 2 200 H 3 16 2 175 H 3 17 1 200 H 2 18 1 175 H 1 19 2 200 H 2 20 2 175 H 1 21 1 200 H 2 22 1 175 H 1 23 2 200 H 2 24 2 175 H 1 Identify each of the following components of the experimental design.

a. factors b. factor levels

c. blocks d. experimental unit

e. measurement unit f. replications

g. treatments

2.15 In each of the following descriptions of experiments, identify the important features of each design. Include as many of the components from Exercise 2.14 as needed to adequately de- scribe the design.

a. A horticulturalist is measuring the vitamin C concentration in oranges in an orchard

on a research farm in south Texas. He is interested in the variation in vitamin C con- centration across the orchard, across the productive months, and within each tree. He divides the orchard into eight sections and randomly selects a tree from each section during October through May, the months in which the trees are in production. During each month, from eight trees he selects 10 oranges near the top of the tree, 10 oranges near the middle of the tree, and 10 oranges near the bottom of the tree. The horticul- turalist wants to monitor the vitamin C concentration across the productive season and determine whether there is a substantial difference in vitamin C concentration in oranges at various locations in the tree.