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18 Cards in this Set
- Front
- Back
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What is the difference between an observational study and an experiment? |
In an experiment, a treatment is applied to part of a population and responses are observed. The researcher in an experiment deliberately influences the responses. In an observational study, a researcher measures characteristics of interest of a part of a population but does not change existing conditions. The researcher in an observational study does not influence the responses. |
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What is the difference between a census and a sampling?
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A census is a count or measure of an entire population. Taking a census provides complete information, but it is often difficult and costly to perform. A sampling is a count or measure of part of a population.
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What is the difference between a random sample and a simple random sample?
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With a random sample, each individual has the same chance of being selected.
With a simple random sample, all samples of the same size have the same chance of being selected. |
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True or False? A double-blind experiment is used to increase the placebo effect. |
The statement is false. Double blinding is used to decrease the placebo effect. |
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True or False? A census is a count of part of a population. |
The statement is false. A census is a count of the entire population. |
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Observational Study or Experiment? Research is conducted to determine if there is a relation between brain cancer and use of cell phones. |
Observational Study because the study examines individuals in a sample, but does not try to influence the variable of interest. |
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A pharmaceutical company wants to test the effectiveness of a new allergy drug. The company identifies 250 females 30-35 years old who suffer from severe allergies. The subjects are randomly assigned into two groups. One group is given the new allergy drug and the other is given a placebo that looks exactly like the new allergy drug. After six months, the subjects' symptoms are studied and compared. Identify the experimental units and treatments used in this experiment. |
The experimental units are the subjects being tested, or the 30- to 35-year-old women. The treatment is applied to part of the population and the responses are observed. |
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A pharmaceutical company wants to test the effectiveness of a new allergy drug. The company identifies 250 females 30-35 years old who suffer from severe allergies. The subjects are randomly assigned into two groups. One group is given the new allergy drug and the other is given a placebo that looks exactly like the new allergy drug. After six months, the subjects' symptoms are studied and compared. Identify a potential problem with the experiment design being used and suggest a way to improve it. Choose the correct answer below. |
There may be a bias on the part of the researcher if the researcher knows which patients were given the real drug. |
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A pharmaceutical company wants to test the effectiveness of a new allergy drug. The company identifies 250 females 30-35 years old who suffer from severe allergies. The subjects are randomly assigned into two groups. One group is given the new allergy drug and the other is given a placebo that looks exactly like the new allergy drug. After six months, the subjects' symptoms are studied and compared How could this experiment be designed to be a double-blind? |
The study would be a double-blind study if both the researcher and the patient did not know which patient received the real drug or the placebo. |
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Using random digit dialing, researchers call 800 people and ask what obstacles keep them from attending town hall meetings. What type of sampling is used? |
Simple random sampling is used, since each number has an equal chance of being dialed, so all samples of 800 phone numbers have an equal chance of being selected. |
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Using random digit dialing, researchers call 800 people and ask what obstacles keep them from attending town hall meetings. What potential sources of bias are present, if any? |
Individuals may not be available when the researchers are calling. Those individuals that are available may not be representative of the population. Telephone sampling only includes people who have telephones. People who own telephones may be older or wealthier on average, and may not be representative of the entire population. Individuals may refuse to participate in the sample. This may make the sample less representative of the population. |
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Questioning students as they leave an academic building, a researcher asks 365 students about their dating habits. What type of sampling is used? |
Convenience sampling is used, because students are chosen due to convenience of location. |
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Questioning students as they leave an academic building, a researcher asks 365 students about their dating habits. What potential sources of bias are present, if any? |
The sample only consists of members of the population that are easy to get. These members may not be representative of the population. Because of the personal nature of the question, students may not answer honestly. |
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After a hurricane, a disaster area is divided into 150 equal grids. Fifty of the grids are selected, and every occupied household in the grid is interviewed to help focus relief efforts on what residents require the most. What type of sampling is used? |
Cluster sampling is used, since the disaster area is divided into grids, and some of those grids are selected and everyone in those grids is interviewed. |
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After a hurricane, a disaster area is divided into 150 equal grids. Fifty of the grids are selected, and every occupied household in the grid is interviewed to help focus relief efforts on what residents require the most. What potential sources of bias are present, if any? |
Certain grids may have been much more severely damaged than others. The grids that are selected may not be representative in terms of damage. Certain grids may have been much more severely damaged than others. Severely damaged grids may have fewer occupied households. |
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Every fourth person entering a cafeteria is asked to name his or her favorite meal. What type of sampling is used? |
Systematic sampling is used, because every fourth person is selected. |
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Every fourth person entering a cafeteria is asked to name his or her favorite meal. What potential sources of bias are present, if any? |
If there is a regular pattern to the people entering the cafeteria, the sample may not be representative. The wording of the question may direct respondents towards a particular meal. |
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The most popular car manufacturer among the 40,000 employees of a company. Would you take a census or use a sampling? |
Sample because the population is too large for it to be practical to record all of the responses. |
