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AP Statistics · Unit 3 · Collecting data · last updated

Collecting data practice questions (AP Statistics)

Unit 3 covers populations and samples, random sampling methods and bias, observational studies versus experiments, the principles of experimental design including blocking, confounding, and the scope of inference. Below are all 3 free AP Statistics questions on it from our free exams, each with a worked answer behind a toggle, then 7 key terms with the formulas typeset, and a door to make an AP Statistics-style paper on this unit from your own notes. The free exams are typeset PDFs with an answer key; the exam downloads without a signup.

Make a practice exam from your notes →Upload your notesAP Statistics style preselected; tick "Unit 3 · Collecting data" on the next screen. Free to try, no card.

Sample questions

All 3 free AP Statistics questions on this unit, from the free AP Statistics Practice Exam and the free AP Statistics Free-Response Practice Questions (FRQ) with Answers. Each answer is behind its own toggle; the whole paper, its PDF and the full answer key are on the exam page.

  1. Question 12 marks · Sampling methods
    A principal wants a sample of 100 students that reflects the proportions of freshmen, sophomores, juniors, and seniors in the school. She randomly selects students separately from each grade, in proportion to grade size. This design is:
    • A.
      A simple random sample
    • B.
      A stratified random sample
    • C.
      A cluster sample
    • D.
      A systematic sample
    • E.
      A convenience sample
    From the free AP Statistics Practice Exam →
  2. Question 22 marks · Experimental design
    In a comparative experiment, the primary purpose of RANDOM ASSIGNMENT to treatments is to:
    • A.
      guarantee the sample represents the population
    • B.
      eliminate all variability between subjects
    • C.
      balance the effects of lurking variables across treatment groups
    • D.
      ensure the placebo effect does not occur
    • E.
      increase the sample size
    From the free AP Statistics Practice Exam →
  3. Question 34 marks · Experimental design
    Experimental design. A researcher wants to determine whether a new liquid fertilizer increases the yield of tomato plants, measured as the total mass of ripe tomatoes in kilograms per plant over a growing season. She has 40 tomato plants of the same variety in a greenhouse. Twenty of the plants are on a bench next to a south-facing window and receive much more sunlight; the other twenty are on a bench on the far side of the greenhouse. Plants given the fertilizer are watered with the fertilizer solution once a week; the other plants are watered with plain water on the same schedule.
    (a)
    Explain why a randomized block design, with the two benches as blocks, is preferable to a completely randomized design for this experiment.
    [1]
    (b)
    Describe how the researcher should carry out the randomized block design. Include how the random assignment would be done and what will be compared.
    [2]
    (c)
    Suppose the fertilized plants produce a significantly higher mean yield than the unfertilized plants. Can the researcher conclude that the fertilizer caused the higher yield? Can she generalize the result to all tomato plants of this variety? Explain both answers.
    [1]
    From the free AP Statistics Free-Response Practice Questions (FRQ) with Answers →

Key terms

The definitions and formulas AP Statistics expects for collecting data, typeset as they appear on the paper.

Simple random sample (SRS)
Every group of nn individuals has the same chance of being chosen. Describe the method concretely on the exam: number the individuals, use a random number generator, ignore repeats.
Stratified, cluster and systematic sampling
Stratified: divide into homogeneous groups and take an SRS from each (reduces variability). Cluster: divide into heterogeneous groups and sample whole groups (saves cost). Systematic: every kkth individual from a random start.
Bias in sampling
Undercoverage (some groups cannot be chosen), nonresponse (chosen individuals do not answer) and response bias (question wording, interviewer effects). Voluntary response and convenience samples are biased by design.
Observational study versus experiment
An experiment imposes treatments; an observational study only records. Only a well-designed experiment can establish cause and effect, because random assignment balances confounding variables.
Principles of experimental design
Comparison of at least two treatments, random assignment of units to treatments, control of other variables, and replication (enough units per treatment). Blinding and placebos control for expectations.
Blocking
Grouping experimental units that are similar on a variable expected to affect the response, then randomising within each block. It reduces variability in the comparison of treatments; it is not the same as stratifying a sample.
Scope of inference
Random sampling lets you generalise to the population; random assignment lets you conclude causation. A study can have one, both or neither, and the conclusion must match.

Frequently asked questions

Are there free collecting data practice questions for AP Statistics?

Yes. 3 questions on collecting data appear in the free AP Statistics Practice Exam and the free AP Statistics Free-Response Practice Questions (FRQ) with Answers, and the sample questions on this page come from them with worked answers. Each exam can be read online or downloaded as a typeset PDF without signing up, and its full answer key is emailed on request.

How do I make an AP Statistics practice paper on collecting data from my notes?

Open the create page with the AP Statistics style preselected, tick "Unit 3 · Collecting data" under the units to cover (or upload your notes and slides on it), choose the question mix and time limit, and generate. You get a typeset PDF in the AP format with a separate answer key, in about a minute. It is free to try, no card needed.

What does AP Statistics expect you to know about collecting data?

Unit 3 covers populations and samples, random sampling methods and bias, observational studies versus experiments, the principles of experimental design including blocking, confounding, and the scope of inference. The terms to have cold: Simple random sample (SRS), Stratified, cluster and systematic sampling, Bias in sampling, Observational study versus experiment, Principles of experimental design. Each is defined below with its formula typeset where one applies.

What is the AP Statistics exam format?

The AP Statistics guide explains the papers, their timing and mark allocation, with a sample question and mark scheme and the common mistakes, and links to the generator with the AP Statistics style preselected.

Other AP Statistics topics

All AP Statistics topics · AP Statistics exam guide · All free practice exams

Make an AP Statistics paper on collecting data from your notes

Open "Pick your exam" with the AP Statistics style preselected and tick "Unit 3 · Collecting data", or upload your notes on it. You get a typeset paper in the AP format with a separate answer key.

Make a practice exam from your notes →Upload your notes