Mid-Chapter Quiz
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What are the differences between a survey, an observational study, and an experiment? Recall the definitions of a population and a sample.
Type of Study: Observational study
Sample: The 15 students in the study
Population: The student body
We want to determine whether the given situation describes a survey, an experiment, or an observational study, then identify the sample and suggest a population from which it may have been selected. Let's do these things one at a time.
We want to determine the type of study being conducted in the described situation.
|
A high school principal wants to test five ideas for a new school mascot. He randomly selects 15 high school students to view pictures of the ideas while he watches and records their reactions. |
To do so, let's first recall the different types of studies and their definitions.
| Study Type | Definition |
|---|---|
| Survey | Data are collected from responses given by members of a sample regarding their characteristics, behaviors, or opinions. |
| Observational Study | Members of a sample are measured or observed without being affected by the study. |
| Experiment | The sample is divided into two groups — an experimental group that undergoes a change and a control group that does not undergo a change. The effect on the experimental group is then compared to the control group. |
In our situation, the data are obtained from observing the students without them being affected by the study. Therefore, the situation describes an observational study.
A population consists of all the members of a group of interest. Since it may be impractical to examine every member of a population, a sample — a subset of the population — is sometimes selected to represent the population. The sample can then be analyzed to draw conclusions about the entire population.
Let's consider our situation again.
|
A high school principal wants to test five ideas for a new school mascot. He randomly selects 15 high school students to view pictures of the ideas while he watches and records their reactions. |
Here, the population is the student body. The sample consists of the 15 randomly selected students who take part in the study.