Internet search engines report many hits, but getting on the first page is critical for a business. A study surveyed 1,232 people from a U.S. online consumer panel in 2002 and independently surveyed a...

Internet search engines report many hits, but getting on the first page is critical for a business. A study surveyed 1,232 people from a U.S. online consumer panel in 2002 and independently surveyed a second panel of 1,137 in 2009. Analysts found that 62% of those surveyed in 2009 clicked on a result on the first page, up from 48% in 2002.

(a) Might the comparison between these two samples be confounded with a hidden factor? If so, identify such a factor.

(b) Find the 95% confidence interval for the difference between the proportion of users who click on a link on the first page of the search results in the two surveys.

(c) What do the results tell businesses about the importance of improving their search rank?