Worksheets · Foundation and Higher

Scatter graphs and predictions

3 exam-style questions. Answers and the mark for each step are on the last page.

1. Question 1Non-calculator · 2 marks

   Each part describes two variables.

   (a) The age of a car and its value. What type of correlation would you expect? (1)

   1. No correlation
   2. Negative
   3. Positive

   (b) The shoe sizes of 30 adults and their scores in the same spelling test. What type of correlation would you expect? (1)

   1. Negative
   2. No correlation
   3. Positive
2. Question 2Non-calculator · 5 marks

   For 12 cars, age x years and value y thousand pounds are plotted on a scatter graph. The line of best fit passes through (1, 16) and (7, 4).

   (a) Find the gradient of the line of best fit. (2)

   (b) Interpret the gradient in this context. (1)

   (c) Use the line to estimate the value, in pounds, of a car that is 5 years old. (2)
3. Question 3Calculator · 3 marks

   (a) A scatter graph relates the length x cm and mass y g of objects of one type. The observed lengths range from 15 cm to 32 cm. A straight line of best fit passes through (17, 42) and (29, 66). Use the line to estimate the mass of an object of length 24 cm. (3)