Slideshow version

Two-way tables display the frequency of two different qualitative variables. Columns are used for one of the variables and rows for the other.

  Morning Evening Total
Coffee 45 15 60
Tea 10 42 52
Total 55 57 112

The intersection shows how many of the data set fit both variables. In the table above, which shows people’s preferred hot drink and what time of day they like to drink it, 60 people prefer coffee and 55 prefer to drink something hot in the morning, but only 45 prefer having coffee in the morning.

You’ll be tasked with reading and creating these, along with analyzing them, which requires careful reading. Here’s two different questions that might be deceptively similar.

  1. What percentage of evening drinkers prefer tea?
  2. What percentage of a tea drinkers have it in the evening?

For the first one, we have to look at the 57 evening drinkers first, then determine that 42 prefer tea. $42/57 \approx 74\%$.

For the second one, we look at the 52 tea drinkers first, then how many prefer the evening. $42/52 \approx 81\%$.

Even though we looked at the 42 evening tea drinkers for both questions, we compared them to different overall categories each time. Be careful that you don’t mix the two up.