Question 8

8. Suppose, out of a certain population, a sample of size 55 and mean 68 was

extracted. By taking = 0.05, carry out[10 Marks]

a) A hypothesis test if the sample mean is different from the population mean of

70 for = 5.

b) A hypothesis test if the sample mean is different from the population mean of

70 for = 7.

Question 9

9. It is believed that it does not matter where you by your car from, whether from

company A or company B, all take the same average time until they are broken

down.

- A sample of 42 taken from company A showed an average time to breakdown of

12 years with standard deviation of 4 years.

- A sample of 51 taken from company B showed an average time to breakdown of

10 years with standard deviation of 6 years.

With = 0.01, test if the belief is true assuming1 =2. [10 Marks]