Q9. A manufacturer of light bulbs is comparing two production processes. They have taken a sample of 1000 bulbs of type A and 1000 bulbs of type B. They have calculated the mean average life and the range of life times for each type (in hours). The results are as follows: | Type A | Type B |
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| Mean (hours) | 12 | 11.2 | | Range (hours) | 3 | 0.4 |
Comment on which is the better bulb. Give a reason to prefer type A and a reason to prefer type B.
This is an explanation of answer A
We chose: bulb A
The idea here is that the average gives a measure of how big something is on average. A higher average in this case is better. The range tells you how spread out the data is. In this case the life times of light bulbs should not be spread out - some are well above average, but some are well below average.
Answer: Type A - last longer. This is an explanation of answer B
We chose: bulb B
We would say that a high range would mean an unreliable light bulb. Type B is better because the lower range says they are more reliable.
Answer: Type B - more reliable. Next question
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