15. The owner of a double glazing company employs 50 salespeople. For the month of June 2019, the total sales made by each salesperson is recorded in the table.
Sales, \(s\) (thousand pounds)
\(10 \lt s \leqslant 20\)
\(20 \lt s \leqslant 30\)
\(30 \lt s \leqslant 40\)
\(40 \lt s \leqslant 50\)
\(50 \lt s \leqslant 60\)
Frequency
0
8
15
18
9
(a) Complete the following cumulative frequency table. [1]
Sales, \(s\) (thousand pounds)
\(s \leqslant 20\)
\(s \leqslant 30\)
\(s \leqslant 40\)
\(s \leqslant 50\)
\(s \leqslant 60\)
Cumulative frequency
0
8
(b) On the grid below, draw a cumulative frequency diagram to show these results. [3]
(c) The owner gives monthly bonuses to the salespeople who have the highest value sales.
Bonus
Top 10% of salespeople
Gold
Next 20% of salespeople
Silver
(i) Use your graph to find the minimum value of sales needed to earn each bonus in June 2019. [2]
Gold bonus £ ………………………… Silver bonus £ …………………………
(ii) Explain why your answers to part (c)(i) may not be accurate. [1]
(d) The box plot shows summary statistics for the month of September 2019.The owner is considering closing the business for 2 days of staff training next year. This can take place in either June or September.
Using the sales data from 2019, should the owner choose to train her staff in June or September?
FT ‘their cf’ provided cumulative; tolerance ± 1mm B1 for 3 or 4 correct plots
All points joined with a smooth curve or with line segments
B1
dep on at least B1 for plots; last point must not be joined to the axis; tolerance ± 1mm
Mark scheme (c)
Scheme
Marks
Comments
(c)(i) Gold bonus: Answer in range 53 000 to 55 000 inclusive
Silver bonus: Answer in range 45 000 to 47 000 inclusive
B2
FT their cf graph for ‘their s’ when cf is 45 and 35 B1 FT for each
If no marks, award SC1 for both Gold bonus in range 53 to 55 and Silver bonus in range 45 to 47
(c)(ii) Valid explanation e.g. ‘The data may not be evenly spread through each group.’ or ‘All the sales in the group 50 to 60 may be 60 000.’ or ‘The raw data is not used.’
E1
Allow e.g. ‘It is estimated because the data is grouped.’ or ‘Because you do not know what each salesperson got.’
Mark scheme (d)
Scheme
Marks
Comments
September and valid evidence/comment e.g. ‘The median sales are lower.’
E1
Evidence must be based on the mathematics and with no contradictions
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