Question

The drying time, in minutes, of two different brands of latex paint were recorded. In a random sample of 6 units of brand 1, the mean average drying time is found to be 70.83 minutes with standard deviation of 15.09. However, for a random sample of 9 units of brand 2, the mean average drying time is found to be 79.33 minutes with standard deviation of 8.08. Assume normal populations. Note: Round all the final numbers to 2 decimal places.

a) (3 points) Create and interpret a 95% confidence interval for the average drying time for brand 1. Note: Do the calculations one time by hand and the other time by R and show your code/output.

b) (3 points) Create and interpret a 95% confidence interval for the average drying time for brand 2. Note: Do the calculations one time by hand and the other time by R and show your code/output.

c) (2 points) In comparing the confidence intervals created in (a) and (b) does there appear to be a difference in the average drying time between brand 1 and brand 2? Explain.

Answer 1

a)

R command :

b)

R command :

c) Since there is a significant difference in lower bound of the two confidence intervals, so there seems to appear to be a significant difference in the average drying time between brand 1 and brand 2.