Question

QUESTION 2

Petronas has developed two blends of gasoline. Managers are interested in estimating the difference in mean gasoline mileage that will be obtained from using the two blends. As part of their study, they have decided to run a test using the Chevrolet Impala automobile with automatic transmissions. They selected a random sample of 100 Impalas using Blend 1 and another 100 Impalas using Blend 2. Each car was first emptied of all the gasoline in its tank and then filled with the designated blend of the new gasoline. The car was then driven 200 miles on a specified route involving both city and highway roads. The cars were then filled and the actual miles per gallon were recorded. The following summary data were recorded:

	Blend 1	Blend 2
Sample Size	100	100
Sample Mean	23.4 mpg	25.7 mpg
Sample St. Dev.	4.0 mpg	4.2 mpg

1. Based on these sample data, compute and interpret the 95 percent confidence interval estimate for the difference in mean mpg for the two blends.

2. To increase productivity, workers went through a training program. The management wanted to know the effectiveness of the program. A sample of seven workers was taken and their daily production rates before and after the training are shown below.

Worker	1	2	3	4	5	6	7
Before	18	23	25	22	20	21	19
After	22	25	27	25	24	19	20

Does the training program effective? Shows your working to support your answer.

Answer 1

Answer a) (-3.444, -1.156)

Answer b)

At 0.05 significance level, there is enough evidence to conclude that the training program is effective.