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Cogito

Probability and Statistics · Chapter 7 · Lesson 1

Practice Worksheet

Samples and Bias

Who did you actually ask?

12 problems · about 21 minutes · TEKS P.S.4.A, S-IC.B.3

NameDate

Figure — use these to answer the problems

A sample should mirror the population. If one group is over-represented here, conclusions will lean that way.
Group A12
Group B12
Group C12
Group A12
Group B12
Group C12
Figure 1

Warm Up

Straightforward practice. Get the method working first.

5 problems

  1. A magazine prints a survey and readers mail it back. Biased? 1 yes, 0 no.

    Answer

  2. Why does a larger sample not fix bias?

    • Bias is systematic, so more data repeats the same error.
    • Because large samples cost too much.

  3. Every individual has an equal chance. Is it a simple random sample? 1 yes, 0 no.

    Answer

  4. Asking friends in the corridor. Convenience sample? 1 yes, 0 no.

    Answer

  5. Sampling within each year group separately. Stratified? 1 yes, 0 no.

    Answer

Build It Up

The same ideas with more to keep track of.

3 problems

  1. A survey in a library about libraries. Biased? 1 yes, 0 no.

    Answer

  2. Which matters more for accuracy? 1 method, 2 size.

    Answer

  3. Is the population the group actually measured? 1 yes, 0 no.

    Answer

Stretch Yourself

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

4 problems

  1. Which are sources of bias?

    • Voluntary response
    • Convenience sampling
    • A leading question
    • Random selection
    • Tick every box that applies.

  2. A phone poll at 10am on a weekday. Does it miss working people? 1 yes, 0 no.

    Answer

  3. The Poll

    An online poll where readers choose to respond. Is this voluntary response bias? 1 yes, 0 no.

    Answer

  4. The Size

    Does a larger sample fix bias? 1 for yes, 0 for no.

    Answer