Yonger Middle Older Row total

Yes 78 49 21 78+49+21=148

No 4 21 46 4+21+46=71

Column total 78+4=82 49+21=70 21+46=67 148+71=219

We the note that the table contains 219 students in total (which is given in the bottom right corner of the above table), while 21 of the 219 students are older and Facebook users (which is given in the row ”Yes” and in the column *Older” of the above table).

\(\displaystyle\frac{{21}}{{219}}=\frac{{7}}{{73}}\sim{0.09589}={9.589}\%\)

Thus 9.589% of the students who responded were older Facebook users.