Electrical Products Ltd. manufactures, among other products, lighting bulbs.
Recently, the company launched a new energy saving lighting bulb. The brand
manager claims that this new model has a mean life of at least 1800 hours. A
quality controller decides to verify the claim and selects a random sample of 50
bulbs. He records the lives of the bulbs as summarized below:
Length of life (hours) Number of bulbs
1000 – 1200 1
1200 – 1400 4
1400 – 1600 8
1600 – 1800 10
1800 – 2000 11
2000 – 2200 7
2200 – 2400 5
2400 – 2600 3
2600 – 2800 1
Required:
Determine if the data support the claim of the brand manager (use
α
= 0.01).
(20 marks)