Question

*EASY QUESTION WORTH 44 POINTS*

Last year, the school made $800 at its cookie sale. This year it made $1,200. Suppose you show these amounts on a bar graph, but you start the vertical scale at $600 instead of $0. Exactly how many times taller will the second bar be than the first? How might this be misleading? EXPLAIN.

Answer 1

Answer: 3 times taller

Step-by-step explanation:

If we started at y = 0, then the bar for last year's sales would be 800 units tall. This is to represent the $800 in sales last year.

However, we start at $600 on the y axis instead. This means the bar for last year's sales would be 200 units tall (because 800-600 = 200).

The bar for this year's sales is 600 units tall (because 1200-600 = 600)

Divide those two heights

600/200 = 3

The second bar is 3 times taller than the first bar.

But wait, the jump from $800 to $1200 is NOT "times 3". The jump is instead "times 1.5" which we can determine like so: 1200/800 = 1.5

In other words, 1.5*800 = 1200

Therefore, the fact we start at 600 on the y axis causes the 2nd bar to be taller than it should be in relation to the first. It causes a distortion.

Check out the diagram below. Figure 1 has us start at 600, which is deceiving. Be careful when you see such a chart in a newspaper for instance. Figure 2 has us start at 0 and now things are in the correct proportion. I used LibreOffice Calc spreadsheet to make the charts.