Comparing two groups of different sizes

In section A, 27 of 40 seeds sprouted (began to grow). In section B, 18 of 25. Which did better?

The rule

Section B did better. A larger share of its seeds sprouted: 72%, against 67.5%.

Compare shares, not counts. A share is a count divided by its own total. Write each share as a percentage.

• Section A: 27 ÷ 40 = 0.675. Then 0.675 × 100 = 67.5, so 67.5%.
• Section B: 18 ÷ 25 = 0.72. Then 0.72 × 100 = 72, so 72%.
• Section B has the smaller count and the bigger share.

Two tests can have different totals too. 33 ÷ 40 = 0.825, so 33 out of 40 is 82.5%. 45 ÷ 60 = 0.75, so 45 out of 60 is 75%. The first test has the larger share.

Try the lab to finish this lesson.