Question

1. The mean lifetime of electric bulbs produced by a company has in the past been 1120

hours with a S.D 125 hours. A sample of 100 bulbs recently chosen from a supply of newly

produced bulbs showed a mean lifetime of 1170 hours. Test the hypothesis that quality of

bulbs has been improved at 5% level of significance.​

Answer 1

Answer:

The mean lifetime of electric bulb produced by a company has in the past been 1120 hours

with a standard deviation of 125 hours. A sample of 8 electric bulbs recently chosen form a supply

of newly manufactured bulbs showed a mean lifetime of 1070 hours. Test the hypothesis that mean

lifetime of the bulbs has not changed using a level of significance of 0.05.