Which experimental principle is she implementing?

Answer: Random assignment She is randomly assigning subjects to treatments without grouping by any variable - random assignment in a completely randomized design.

What kind of design is this?

Answer: Randomized block design with gender as the blocking variable Subjects are first separated into blocks (men, women) and then randomly assigned to treatments within each block - a randomized block design.

What design is shown?

Answer: Randomized block design with two blocks and three treatments Subjects are first separated into blocks (Young/Old), then randomly assigned to one of three treatments within each block. This is a randomized block design.

AP Statistics · Topic 3.6

Selecting an Experimental Design Practice

Part of Collecting Data.(VAR-3.B)

Practice questions

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Sample questions

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Sample 1difficulty 1/5
$A teacher has 30 students and wants to randomly assign 15 to each of two methods. She writes each student's name on a slip of paper, mixes them in a hat, and draws 15 names for Method A; the rest go to Method B.$
$Which experimental principle is she implementing?$
- A
  $Random assignment$
  check_circle
- B
  $Replication$
- C
  $Blocking$
- D
  $Stratification$
Why
$She is randomly assigning subjects to treatments without grouping by any variable - random assignment in a completely randomized design.$
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Sample 2difficulty 2/5
$A study of two exercise programs has 60 men and 60 women. Researchers randomly assign 30 men to each program and 30 women to each program.$
$What kind of design is this?$
- A
  $Randomized block design with gender as the blocking variable$
  check_circle
- B
  $Stratified random sample$
- C
  $Completely randomized design$
- D
  $Matched-pairs design$
Why
$Subjects are first separated into blocks (men, women) and then randomly assigned to treatments within each block - a randomized block design.$
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Sample 3difficulty 2/5
$The diagram describes a study of three treatments stratified by age.$
$What design is shown?$
- A
  $Randomized block design with two blocks and three treatments$
  check_circle
- B
  $Matched-pairs design$
- C
  $Stratified sampling design$
- D
  $Completely randomized design with six treatments$
Why
$Subjects are first separated into blocks (Young/Old), then randomly assigned to one of three treatments within each block. This is a randomized block design.$
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Sample 4difficulty 2/5
$A skin-care company tests a new lotion against a competitor by applying one lotion to each subject's left cheek and the other to the right cheek (with side randomized). After 4 weeks, dermatologists rate skin smoothness on each cheek.$
$Which design is described?$
- A
  $Observational study$
- B
  $Completely randomized design$
- C
  $Matched-pairs design$
  check_circle
- D
  $Randomized block with multiple blocks per subject$
Why
$Each subject receives both treatments simultaneously, with side randomized; each subject is the matched pair. Comparisons within subjects control for individual skin differences.$
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Sample 5difficulty 2/5
$A placebo is$
- A
  $An inert substance designed to look like the treatment$
  check_circle
- B
  $An active drug$
- C
  $An outlier$
- D
  $A confounder$
Why
$Placebos help isolate the effect of psychological expectation.$
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