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Grade 8 · Math · Unit 12 of 13

Reading Graphs Critically

Pick the right graph and spot misleading ones

What your child practises

Choosing the best graph for a set of data and noticing when a graph or survey could mislead: a squeezed scale, a biased sample or a loaded question.

Alberta Curriculum learning outcome: SP1 · choosing and critiquing circle graphs, line graphs, bar graphs and pictographs, including bias and misleading scales

Sample questions

A taste of this unit. In the app, questions change every time and get easier or harder to match your child.

  1. Question 1

    A circle graph has three sectors of 50%, 20% and 10%. One sector is left. What percent is it?

    answer box%

    Show answer

    20 %

    Hint: The whole circle is 100%. 100 − 50 − 20 − 10 = 20.

  2. Question 2

    A pictograph uses bigger and bigger pictures to show bigger amounts. Why can this mislead readers?

    • Pictures are always accurate.
    • Readers cannot see the pictures.
    • It makes all the amounts the same.
    • A larger picture covers more area, so it looks like a much larger amount.
    Show answer

    A larger picture covers more area, so it looks like a much larger amount.

    Hint: Compare heights or counts of equal-sized symbols, not areas of different-sized pictures.

  3. Question 3

    Five students out of a school of 600 are surveyed. Why is the conclusion weak?

    • The sample is too small to represent the school.
    • The school is too small.
    • Five is too many.
    • Surveys can never be used.
    Show answer

    The sample is too small to represent the school.

    Hint: A larger, fairly chosen sample gives more reliable results.

  4. Question 4

    In a circle graph of 500 survey responses, the 'walk to school' sector is 35%. How many responses is that?

    answer box

    Show answer

    175

    Hint: 35% of 500 = 35/100 × 500 = 175.

  5. Question 5

    Which graph is best for comparing the number of students in each school club?

    • a circle graph
    • a line graph
    • a bar graph
    • a scatter plot
    Show answer

    a bar graph

    Hint: A bar graph compares amounts for separate categories.

  6. Question 6

    Which source is the most reliable for the population of Alberta?

    • a post by an unknown account
    • a friend's guess
    • an advertisement
    • a national statistics agency
    Show answer

    a national statistics agency

    Hint: Reliable data comes from a trustworthy organization that explains how it counted.

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