Population
Entire group of individuals of interest
Sample
Part of the population actually studied for information
Census
A count and categorization of all members of a population
Sample design
Method used to select the sample
A newspaper in New Jersey conducted a poll of its readers to obtain their opinions on whether Michael Jordan would return to play basketball again in the NBA. 40% of the eligible readers participated. This is an example of a(n)
Sample survey
A high school guidance counselor decided to compare PSAT results for the male and female students in the junior class at your high school. Which is the best technique for gathering the data needed?
Census
Creating a sample of students by starting with the second name in the student directory and selecting every 15th name best describes
Systematic sampling
A study found that playing classical music increased worker productivity. However, the researchers were not aware that the workers knew about the study while it was in progress. Since the increase in productivity may have been due to the workers' knowledg
A lurking variable
Creating a sample of students by first dividing the entire student body into four groups (freshmen, sophomores, juniors, and seniors) and then selecting a sample random sample (SRS) from each of the four groups is an example of
Stratified sampling
Voluntary response sample
Sample is made up of volunteers, and thus may not be representative of the population
Convenience sample
Sampling from those easiest to reach, in danger of bias
A survey on youth and smoking contacted by telephone 300 smokers and 300 non smokers, all 14 to 22 years of age. What kind of survey is this?
A sample survey (with a stratified sample: smokers and non smokers)
Does air pollution induce DNA mutations in mice? Starting with 40 male and 40 female mice, 20 of each sex were housed in a polluted industrial area downwind from a steel mill. The other 20 of each sex were housed at an unpolluted rural location 30 kilomet
A block design (blocked by gender)
Probability sample
Gives each member of the population a known chance (greater than 0) to be selected (though the chances are not necessarily the same)
Simple random sample (SRS)
Consists of n individuals; chosen in such a way that every set of n individuals has equal chance of being selected
Which of the following are characteristics of a sound experimental design?
1. Compare several treatments to control the effects of lurking variables on the response
2. Use randomization to assign subjects to treatments
3. To reduce chance variation in the
1, 2, and 3
Systematic random sample
Randomly assigning individuals in a population with a #; randomly select one #, then select every individual afterwards by following a rule for entire sample
A study is conducted on a sample of arthritis sufferers to test a new arthritis drug against aspirin. The subjects are randomly assigned to one of 2 groups: a group that receives aspirin and another that receives the new drug. The subjects have no knowled
Blinding
A furniture maker buys hardwood in large batches. The supplier is supposed to dry the the wood before shipping. The furniture maker chooses five pieces of wood from each batch and tests their moisture content. If any piece exceeds 12% content, the entire
Hardwood from the supplier in this batch
A market research firm is hired by a nationally known cosmetics company to test new formulations of moisturizer. Using their extensive list of possible subjects, the market researchers first divide the subjects into 5 age groups and then randomly select n
Stratified sampling
In order to take a sample of 90 members of a local gym, I first divide the members into
men and women, and then take a simple random sample of 45 men and a separate
simple random sample of 45 women. This is an example of a
Stratified random sample
A marketing research firm wishes to determine if the adult men in Laramie, Wyoming, would be interested in a new upscale men's clothing store. From a list of all residential addresses in Laramie, the firm selects a simple random sample of 100 and mails a
All adult men in Laramie, Wyoming
A statistics student wishes to test the strength of various brands of paper towel. He chooses 5 brands and selects 6 towels from each brand. He numbers them 1-30. He randomly selects a towel and places it in an embroidery hoop. Exactly 10 ml of water and
A brand of paper towel
An educator wants to compare the effectiveness of computer software that teaches reading with that of a standard reading curriculum. She tests the reading ability of each student in a class of fourth graders, then divides them into two groups. One group u
Learning method (computer or standard) and reading ability (increased or not)
100 subjects are randomly assigned to two types of diet pills. 50 people are given type A pill and a strict diet to maintain. 50 people are given type B pill with no specific diet instructions. In a second study, people responded to a questionnaire asking
The first is an experiment while the second is an observational study
Stratified random sample
Divide population into random strata then choose separate SRS in each stratum and combine to form full sample
Describe the sample bias:
The person chosen for a survey cannot be contacted in five calls.
Nonresponse
Describe the sample bias:
Interviewers choose people walking by on the sidewalk to interview.
Convenience sample
Describe the sample bias:
The telephone directory is used for a sampling frame.
Undercoverage
In order to select a sample of undergraduate students in the United States, I select a
simple random sample of four states. From each of these states, I select a simple random sample of two colleges or universities. Finally, from each of these eight colle
Multistage sampling
A public opinion poll in Ohio wants to determine whether registered voters in the state
approve of a measure to ban smoking in all public areas. They select a simple random
sample of 50 registered voters from each county in the state and ask whether they
A stratified sample
A simple random sample of 1200 adult Americans is selected, and each person is asked the following question:
In light of the huge national deficit, should the government at this time spend additional
money to establish a national system of health insuranc
Probably understates the percentage of people that favor a system of national health insurance
A news release for a diet products company reports: "There's good news for the 65
million Americans currently on a diet." Its study showed that people who lose weight
can keep it off. The sample was 20 graduates of the company's program who endorse it
in
Biased, overstating the effectiveness of the diet