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Figure This!

Quick Answer:

Half of the items are cheaper at the grocery store.

The convenience store’s prices seem lower overall, however, due to the big difference in the prices of seltzer.



Complete Solution:

There are several ways to approach this problem. For example, using the hint, draw the line y = x on a copy of the graph. A point below the line indicates that the item’s price at the convenience store was less than its price at the grocery store. For example, the point for Ginger ale is below the line. It cost about $1.40 in the grocery but only $1.00 in the convenience store. Four of the eight points are below the line, indicating that the grocery store was more expensive for half the items, while the convenience store was more expensive for half the items.

Alternate Approcach
Another way to examine pricing at the two stores uses the vertical distance from each data point to the line y = x. On the scatterplot, this distance represents the difference in prices at the two stores. The table below lists the estimated difference for each item in the column for the store where it costs more. The sums of the differences show that prices in the grocery store are higher overall.

Approximate Difference at Most Expensive Store
Grocery Convenience












Evian™ $0.40  
Tonic   $0.40
Ginger Ale $0.40  
Total $2.40 $1.90
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