A farm-equipment manufacturer wants to compare the average daily downtime (in minutes) for two sheet-metal stamping machines located in two different factories. Investigation of company records for 100 randomly selected days on each of the two machines gave the following 95% confidence interval for the difference between average daily downtime in factories A and B: (1.968, 2.674).

This means:

a. 95% of the time, the difference in daily average downtime between the factories is between 1.968 minutes and 2.674 minutes.

b. There is a 95% chance that the difference in daily average downtime is between 1.968 minutes and 2.674 minutes.

c. We are 95% certain that the average daily downtime between factories is the same.

d. We are 95% certain that the average daily downtime differs between the two factories.

e. Factory A experiences downtime about twice as often as factory B.