Q1) Below find the records of 12 randomly selected used pickup trucks (none used commercially) and 11 randomly selected used passenger cars, the time (in years) that they were kept by the original owner before being sold: Used pickup trucks 2.9 2.5 3 5 4.2 3.1 3.3 4 6 5.3 3.8 4.5 Used passenger cars 3 2.2 2.8 4.3 4 3.3 2.9 2.1 2 3.1 3 It is known that the standard deviation of used pickup trucks is 2 years and of used passenger cars is 1 year. (a) Investigate, at the 5% significant level, whether the mean time (in years) that used pickup trucks were kept by the original owner before sold is larger than used passenger cars. (b) What assumption is needed to perform the test in (a). (c) Construct the 96% confidence interval for the mean difference of time (in years) were kept by the original owner before sold between used passenger cars and used pickup trucks. Use this confidence interval to tell whether there is difference in the mean time (in years) between these 2 types of vehicles