A pet food producer fills 25-pound bags of dog food on two different production lines located in separate cities. In an effort to determine whether differences exist between the average fill rates for the two lines, a random sample of 18 bags from line 1 and a random sample of 22 bags from line 2 were recently selected. Each bag's weight was measured and the accompanying table reports the summary measures from the samples. Assume the two lines are normally distributed with equal variances. Complete parts a through c below. Production Line 1 Production Line 2
Sample size n 18 22
Sample mean x 24.75 25.23
Sample standard deviation, s 0.05 0.09

Required:
a. Calculate the point estimate for the difference between the population means of the two lines.
b. Develop an 80% confidence interval estimate of the true mean difference between the two lines.