Surveys and Observational Studies
A free Statistics and Data Analysis lesson from the “Collecting Data” unit, with a worked example and practice problems including step-by-step solutions.
Surveys collect responses, and observational studies record what happens naturally. They can reveal patterns and associations, but without random assignment they usually cannot prove causation. This lesson builds the habit of reading the context first, choosing the right statistical tool, calculating carefully, and then writing what the result means. By the end, students should be able to do the computation and explain why that computation answers the question.
What you'll learn
- Identify survey wording issues
- Describe observational study limits
- Explain association without overclaiming causation
Worked example
Problem. A study records students' sleep time and quiz scores without assigning sleep schedules. What type of study is this?
- The researcher only records what happens naturally.
- No treatment is assigned, so this is observational.
Answer: observational study
Lesson preview: this page shows 5 practice items. The interactive activity contains 28 practice items and 15 quiz items (multiple choice). Counts include repeated prompts and variants.
Practice problems
1. Practice case A: A question says, 'Would you support the helpful new schedule?' What is the concern?
Choices: the sample is automatically random · the study is double-blind · the result proves causation · the wording is biased
Show solution
- Loaded words push the respondent toward an answer.
- Survey questions should be neutral.
Answer: the wording is biased
2. Practice case B: Which wording is best for measuring opinion without leading?
Choices: How satisfied are you with the current lunch schedule? · Do you love the improved lunch schedule? · Why is the lunch schedule so inconvenient? · Should we keep the obviously better schedule?
Show solution
- Neutral wording does not suggest the desired answer.
- It lets respondents answer honestly.
Answer: How satisfied are you with the current lunch schedule?
3. Practice case C: A researcher compares students who already participate in sports with those who do not. No one is assigned to a group. What can this study usually show?
Choices: that all variables are categorical · association, not definite causation · cause and effect with certainty · the exact population parameter
Show solution
- Observational studies can reveal patterns.
- Without random assignment, causation is harder to justify.
Answer: association, not definite causation
4. Practice case D: A teacher emails a survey to a full class, but only a few students answer. What is the main concern?
Choices: random assignment · a larger margin of error only · nonresponse bias · placebo effect
Show solution
- People who do not respond may differ from those who do.
- That can bias the result.
Answer: nonresponse bias
5. Practice case E: A survey asks students to estimate screen time from memory. Which issue could affect accuracy?
Choices: random assignment · chi-square association · placebo control · recall error
Show solution
- People may not remember details perfectly.
- That can affect survey data.
Answer: recall error
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