Scatter Plots and Bivariate Data Quiz

Grade 8 · Math · Quiz

Practice analyzing scatter plots, trend lines, and data associations.

Questions

1. As temperature rises, ice cream sales rise. This shows:

   1. Negative association
   2. No association
   3. Positive association
   4. Causation
   Show answer

   Answer: Positive association

   Both variables (temperature and sales) increase together.

2. A strong association means data points cluster tightly around the trend line.

   Show answer

   Answer: True

   Strength of association = how tightly points cluster around the trend line.

3. A scatter plot with no clear trend shows ___ association.

   Show answer

   Answer: no

   No pattern means the variables are not related.

4. Trend line: y = -3x + 50. The negative slope tells us:

   1. y increases as x increases
   2. y decreases as x increases
   3. No relationship
   4. Data is random
   Show answer

   Answer: y decreases as x increases

   Negative slope means the trend goes downward.

5. Line of best fit: y = 4x + 2. Predict y when x = 5.

   1. 22
   2. 25
   3. 30
   4. 42
   Show answer

   Answer: 22

   y = 4(5) + 2 = 20 + 2 = 22.

6. An outlier must always be removed from the data set.

   Show answer

   Answer: False

   Outliers should be investigated — they may be errors OR genuinely exceptional cases.

7. 'Wearing big shoes causes tallness' confuses correlation with ___.

   Show answer

   Answer: causation

   Shoe size and height are correlated but shoe size does not cause height.

8. Which describes the strongest negative association?

   1. Random scatter
   2. Points loosely trending down
   3. Points tightly on a downward line
   4. All points above x-axis
   Show answer

   Answer: Points tightly on a downward line

   Strong = tight clustering; negative = downward trend.

9. A trend line has positive slope. This means:

   1. As x increases y decreases
   2. As x increases y increases
   3. x and y are equal
   4. No pattern
   Show answer

   Answer: As x increases y increases

   Positive slope: rise/run is positive — y goes up as x goes up.

10. You can use a line of best fit to predict values outside the data range.

    Show answer

    Answer: True

    Extrapolation uses the trend line beyond the data range, though reliability decreases with distance.

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