100 electric light bulbs of Brand A were tested to find how long each bulb lasted. The results are summarised in the table below. Time (t hours) | t≤50 | 50<t≤100 | 100<t≤150 | 150<t≤200 | 200<t≤250 | 250<t≤300 | 300<t≤350 Number of bulbs | 2 | 2 | 10 | 40 | 30 | 14 | 2

1. (a)Complete the cumulative frequency table. Time (t hours) | t≤50 | t≤100 | t≤150 | t≤200 | t≤250 | t≤300 | t≤350 Cumulative frequency | 2 | 4 | | | | | 100[1]
2. (b)On the grid, draw a smooth cumulative frequency curve to represent this information. Label this curve Brand A. [Figure 10.1][2]
3. (c)(i)Use your graph to estimate the median.[1]
4. (c)(ii)Use your graph to estimate the interquartile range.[2]
5. (d)100 Brand B bulbs gave the following results. 4 bulbs lasted 50 hours or less. The longest time any bulb lasted was 300 hours. The median is 250 hours. The upper quartile is 275 hours. The interquartile range is 75 hours. On the grid, draw and label the cumulative frequency curve for the Brand B bulbs. [Figure 10.1][4]
6. (e)Using your graph, estimate the number of Brand A bulbs that lasted 275 hours or less.[1]
7. (f)Complete the statement below. Brand ............ had ............ more bulbs that lasted longer than 275 hours than Brand .............[1]

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