1. A manufacturer claims that the average lifetime of his lightbulb is 3 years or 36 months. The standard deviation is 8 months. Fifty bulbs are selected, and the average life expectancy is found to be 32 months. Should the manufacturer statement be rejected at level of significance 0.01?

Hypotheses:

Null hypothesis:

Alternative:

Test Statistic:

Level of Significance :

Decision Rules:

a.

b.

Computation:

Interpretation of the result: (3 points)

1. A test on car braking reaction times for men between 18 and 30 years old has produced a mean and standard deviation of 0.61 and 0.143 seconds respectively. When 40 male drivers of this age group were randomly selected and tested for their braking reaction times, a mean of 0.587 second came out. At the level of significance 0.05, test the claim of the driving instructor that his graduates had faster reaction time.

Hypotheses:

Null hypothesis:

Alternative:

Test Statistic:

Level of Significance :

Decision Rules:

a.

b.

Computation:

Interpretation of the result: