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Cogito

AP Statistics · Chapter 4 · Lesson 3

Practice Worksheet

Comparing Two Means

Paired data or two independent samples?

12 problems · about 22 minutes · UNC-4.Y, DAT-3.G

NameDate

Figure — use these to answer the problems

For paired data, these values would be the differences rather than the raw measurements.
020
  • Minimum2
  • Lower quartile3
  • Median5
  • Upper quartile7
  • Maximum8
  • Interquartile range4
Difference 12
Difference 24
Difference 35
Difference 46
Difference 58
Figure 1

Warm Up

Straightforward practice. Get the method working first.

5 problems

  1. Paired data with 12 subjects. What are the degrees of freedom?

    Answer

  2. How do you decide whether a design is paired?

    • Ask whether each value in one group has a natural partner in the other.
    • Check whether the two groups are the same size.

  3. Two unrelated groups of 30 and 40 people. Paired or two-sample? 1 or 2?

    Answer

  4. Left and right hand strength on the same people. 1 paired, 2 two-sample.

    Answer

  5. Paired data with 15 subjects. Degrees of freedom for the t procedure?

    Answer

Build It Up

The same ideas with more to keep track of.

3 problems

  1. Can two-sample groups have different sizes? 1 yes, 0 no.

    Answer

  2. Can paired groups have different sizes? 1 yes, 0 no.

    Answer

  3. Differences 2, 4, 6. What is their mean?

    Answer

Stretch Yourself

Mixed problems. Work out what kind of question it is before you start.

4 problems

  1. Sort each study by its design.

    Write each item under the heading it belongs to: Before and after on the same subjects · Matched twins, one in each condition · A treatment group and a separate control group · Two unrelated schools compared

    Paired

    Two-sample

  2. Paired data with 25 subjects. Degrees of freedom?

    Answer

  3. The Design

    Before and after readings on the same 20 patients. Paired or two-sample? 1 paired, 2 two-sample.

    Answer

  4. The Count

    20 patients measured twice. How many differences are analysed?

    Answer