Collecting Data Checkpoint
A free Statistics and Data Analysis lesson from the “Collecting Data” unit, with a worked example and practice problems including step-by-step solutions.
This checkpoint reviews sampling, bias, surveys, observational studies, experiments, control, blinding, simulation, and scope of inference.
What you'll learn
- Review the major skills from this part of the course
- Choose an appropriate statistical method
- Explain results in context
Worked example
Problem. A sample statistic describes:
- Worked Example: First identify exactly what the question is asking: A sample statistic describes:
- Compare each answer choice with the calculation or rule, and eliminate choices that do not satisfy the condition.
- A statistic is computed from sample data.
- A parameter describes the population.
Answer: the sample
Practice problems
1. Review case A: A sample statistic describes:
Choices: the sample · the entire population with certainty · the placebo · the null hypothesis
Show solution
- Checkpoint Review: First identify exactly what the question is asking: A sample statistic describes:
- Compare each answer choice with the calculation or rule, and eliminate choices that do not satisfy the condition.
- A statistic is computed from sample data.
- A parameter describes the population.
- Verify the selected choice by checking that it satisfies the original prompt and that the other choices fail the same test.
Answer: the sample
2. Review case B: Random sampling mainly helps a study:
Choices: prove causation by itself · remove every outlier · make all variables categorical · generalize to a population
Show solution
- Checkpoint Review: First identify exactly what the question is asking: Random sampling mainly helps a study:
- Compare each answer choice with the calculation or rule, and eliminate choices that do not satisfy the condition.
- Random sampling helps the sample represent the population.
- That supports generalizing results.
- Verify the selected choice by checking that it satisfies the original prompt and that the other choices fail the same test.
Answer: generalize to a population
3. Review case C: Voluntary response samples are risky because:
Choices: they have no variables · they prove causation · people with strong opinions may be overrepresented · they are always too large
Show solution
- Checkpoint Review: First identify exactly what the question is asking: Voluntary response samples are risky because:
- Compare each answer choice with the calculation or rule, and eliminate choices that do not satisfy the condition.
- Voluntary samples depend on who chooses to respond.
- That can create bias.
- Verify the selected choice by checking that it satisfies the original prompt and that the other choices fail the same test.
Answer: people with strong opinions may be overrepresented
4. Review case D: Random assignment mainly helps an experiment:
Choices: turn a table into a graph · compare treatments fairly · choose a representative sample · increase every p-value
Show solution
- Checkpoint Review: First identify exactly what the question is asking: Random assignment mainly helps an experiment:
- Compare each answer choice with the calculation or rule, and eliminate choices that do not satisfy the condition.
- Random assignment balances other factors across treatment groups.
- That supports fair treatment comparison.
- Verify the selected choice by checking that it satisfies the original prompt and that the other choices fail the same test.
Answer: compare treatments fairly
5. Review case E: A placebo is:
Choices: a fake treatment used for comparison · the sample mean · the population size · a residual from a model
Show solution
- Checkpoint Review: First identify exactly what the question is asking: A placebo is:
- Compare each answer choice with the calculation or rule, and eliminate choices that do not satisfy the condition.
- A placebo looks like a treatment but lacks the active ingredient.
- It helps measure expectation effects.
- Verify the selected choice by checking that it satisfies the original prompt and that the other choices fail the same test.
Answer: a fake treatment used for comparison
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