8th grade statistics and probability

Question 1

A two-way table: Year 7 — cats 17, dogs 18; Year 8 — cats 7, dogs 10. How many students are in the table altogether?

Answer 

Question 2

Data was collected for x from 1 to 8, and the line of best fit is y = 2x + 18. Fatima uses it to predict y when x = 47. Why should Fatima be careful?

• A. The answer will be a decimal
• B. The line has a positive slope
• C. Lines of best fit can never be used
• D. x is far outside the data range, so the trend may not continue

Question 3

Which point is an outlier in this scatter plot?

• A. (6, 7)
• B. (4, 7)
• C. (8, 9)
• D. (2, 13)

Question 4

Kai plotted two measurements for 8 plants in a scatter graph. What type of correlation does it show?

• A. Positive
• B. Negative
• C. No correlation

Question 5

The line of best fit for the cost of a taxi ride (y, in currency units) against distance (x, in km) is y = 2x + 11. What does 11 represent?

• A. The cost of a 11 km trip
• B. The predicted cost for a 0 km trip (the starting charge)
• C. The longest possible trip
• D. The cost per km

Question 6

What association would you expect between: Hours spent revising and test score?

• A. Positive
• B. Negative
• C. None

Question 7

The line of best fit for test score (y) against hours of practice (x) is y = 3x + 44. Predict the score after 2 hours.

Answer 

Question 8

For plants, the line of best fit of height in cm (y) against age in weeks (x) is y = 2x + 39. What does 2 mean?

• A. Plants grow 39 cm per week
• B. Plants grow about 2 cm per week
• C. Plants grow for 2 weeks
• D. Plants are 2 cm tall at the start

Question 9

Year 9 survey. Have a pet: 10 with a phone, 27 without. No pet: 8 with a phone, 24 without. Of the students WITH a phone, what fraction have a pet? Give a fraction in simplest form.

Answer (as a fraction)

Question 10

The line of best fit for hours studied (x) and test score (y) is y = 5x + 9. Predict the score for 9 hours of study.

Answer 

Question 11

In Class X, 8 of 40 students bike to school. In Class Y, 20 of 50 students bike to school. Which class has the higher proportion of cyclists?

• A. X
• B. Y
• C. The same

Question 12

Year 7 — cats 20, dogs 10; Year 8 — cats 14, dogs 13. A Year 7 student is picked at random. What is the probability they prefer cats? Give a fraction in simplest form.

Answer (as a fraction)

Question 13

A line of best fit is y = 2x + 5. For which x does it predict y = 19?

Answer 

Question 14

What kind of association does the scatter plot show?

• A. Positive association
• B. Negative association
• C. No association

Question 15

Does this scatter plot show a linear or a nonlinear association?

• A. Linear
• B. Nonlinear

Question 16

80 students in Club A and 30 students in Club B were asked if they recycle at home. 48 in Club A and 6 in Club B said yes. What percentage of Club B recycle at home?

Answer