The table shows the times, in seconds, taken for each of 12 members of an athletics club to run 400 metres and 800 metres. Time for 400m (seconds) 49 62 58 52 51 68 56 63 50 61 53 55 Time for 800m (seconds) 118 132 124 121 124 130 129 138 126 131 119 127
- (a)(i)On the grid, complete the scatter diagram. The first six points have been plotted for you.[2]
- (a)(ii)Runners who took less than 55 seconds to run 400 metres and less than 125 seconds to run 800 metres are selected to enter an athletics competition. How many of these runners are selected for the competition?[1]
- (a)(iii)What type of correlation does the scatter diagram show?[1]
- (a)(iv)Draw a line of best fit on the scatter diagram.[1]
- (a)(v)Another runner took 65 seconds to run 400 metres. Use your line of best fit to estimate how long they would take to run 800 metres.[1]
- (b)(i)50 members of the athletics club attempted the high jump. The table summarises the heights, in centimetres, of their jumps. Height (h cm) 140 ≤ h < 145 145 < h ≤ 150 150 < h ≤ 155 155 < h ≤ 160 160 < h < 165 Frequency p 10 15 13 q The athletics coach uses the mid-interval values to calculate an estimate of the mean height jumped by the 50 athletes. His estimate of the mean is 153.6cm. Explain why p+q = 12.[1]
- (b)(ii)Show that 142.5p+162.5q = 1870.[2]
- (b)(iii)Find the value of p and the value of q. Show your working.[3]
This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.
Mark scheme
Marking points from the official mark scheme (Oct/Nov 2019). The mark or mark type is shown in brackets.
- [2] 6 points plotted correctly
- [2] B1 for 3, 4 or 5 points plotted correctly
- [1] 4
- [1] Positive
- [1] Ruled line of best fit
- [1] Their time for 800 m at 65 s for 400 m
- [1] Strict FT their straight line of best fit
- [1] p+10+15+13+q = 50 oe
- [2] 142.5p+147.5×10+152.5×15+157.5×13+162.5q=153.6×50 oe
- [2] simplified to 142.5p+162.5q = 1870
- [2] B1 for 142.5p, 147.5×10, 152.5×15, 157.5×13 and 162.5q seen or for 153.6×50 seen
- [3] Correct method to eliminate one variable
- [3] [p =]4
- [3] [q =]8
- [3] A2 A1 for one correct
- [3] or B1 only for correct answers without algebraic method
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