EXAMPLE 7.1

Watching traditional television. The Nielsen Company is a global information and media company and one of the leading suppliers of media information. In their annual Total Audience Report, the Nielsen Company states that adults age 18 to 24 years old average 18.5 hours per week watching traditional television.¹ Does this average seem reasonable for college students? They tend to watch a lot of television, but given their unusual schedules, they may be more likely to binge-watch or stream episodes after they air. To investigate, let’s construct a 95% confidence interval for the average time (hours per week) spent watching traditional television among full-time U.S. college students. We draw the following SRS of size 8 from this population:

The sample mean is

and the standard deviation is

with degrees of freedom n − 1 = 7. The standard error is

From Table D, we find t* = 2.365. The 95% confidence interval is

= 14.5 ± (2.365)(5.252)

= 14.5 ± 12.421

= (2.08, 26.92)

We are 95% confident that among U.S. college students the average time spent watching traditional television is between 2.1 and 26.9 hours per week.