Populations, Samples, Parameters, and Statistics
A free Statistics and Data Analysis lesson from the “Collecting Data” unit, with a worked example and practice problems including step-by-step solutions.
A population is the full group of interest; a sample is the part actually observed. A parameter describes a population, while a statistic describes a sample. 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
- Distinguish population from sample
- Distinguish parameter from statistic
- Use notation and language precisely
Worked example
Problem. A school wants to learn about homework time for all 9th graders and surveys 90 randomly chosen 9th graders. In this study, what is the sample?
- The sample is the group actually measured.
- Here the measured group is the 90 chosen 9th graders.
Answer: the 90 randomly chosen 9th graders
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 coach wants to know how all team families feel about practice times and surveys 30 families. What is the population?
Choices: the full group the study wants to learn about · the people surveyed only · the survey question · the sample statistic
Show solution
- The population is the full group of interest.
- The sample is only the group actually surveyed.
Answer: the full group the study wants to learn about
2. Practice case B: A teacher surveys 18 students from one class period. What is the sample?
Choices: everyone the study might care about · the population parameter · the conclusion · the people actually surveyed
Show solution
- The sample is the observed group.
- It is smaller than or equal to the population.
Answer: the people actually surveyed
3. Practice case C: A sample of 75 students has an average screen time of 3.4 hours. The 3.4 hours is a:
Choices: treatment · placebo · sample statistic · population parameter
Show solution
- A statistic is computed from a sample.
- A parameter describes the whole population.
Answer: sample statistic
4. Practice case D: A complete roster shows that 18% of all club members are seniors. The 18% is a:
Choices: survey bias · population parameter · sample statistic · random assignment
Show solution
- A parameter describes the whole population.
- The wording says all members of the group were included.
Answer: population parameter
5. Practice case E: In a spreadsheet where each row is one order, what is one case?
Choices: one individual row being studied · the average of a column · the whole population only · the answer choice
Show solution
- Cases are the individuals or items represented by rows.
- Variables describe something about each case.
Answer: one individual row being studied
Practice this interactively with instant feedback and an AI tutor.
Practice Populations, Samples, Parameters, and Statistics Take the free placement check