Advertisers fear that users of DVRs (digital video recorders) will “fast forward†past commercials when they watch a recorded program. A leading British pay television company told its advertisers that this effect might be offset because DVR users watch more TV. A sample of 25 DVR users showed a daily mean screen time of 2 hours and 30 minutes with a standard deviation of 14 minutes, compared with a daily mean of 2 hours and 18 minutes with a standard deviation of 11 minutes for a sample of 25 non-DVR users. (a-1) Construct a 99 percent confidence interval for the difference in mean TV watching.