Idea 21of 22Builds onOut of the number asked
Compare shares, not counts
How do you compare two groups that are different sizes?
Today you'll discover
- why a bigger count can be a smaller part
- how to compare fairly
- what the same length shows
Think firstRoom 12 has 12 walkers; Room 14 has 15
Room 12 has 12 walkers; Room 14 has 15. Which class has more walkers, for its size?
Decide first, then press Next. Watch the shorter class stretch to match the longer one.
Two bars. First only the walkers: Room 12, 12; Room 14, 15, the longer bar. Then each class's whole: 20 boxes and 30 boxes. Then both wholes stretched to the same length, so Room 12's filled part is longer. Then marks every 10%: Room 12, 60%; Room 14, 50%. The last step shows 18 of 25 Grade 5s and 21 of 35 Grade 6s.
See the whole ideathe big idea and the key word, in one place
The big idea
Groups of different sizes compare fairly by share, a relative frequency, not by count.
Walkers
By count, Room 14 wins: 15 against 12. By share, Room 12 wins: 60% against 50%.
Easy to get wrongOnly compare counts when the groups are the same size. Otherwise turn each into a fraction, decimal or percent first.
Key word
- share
- a part out of its whole, as a fraction, decimal or percent
Ready to use it?
- Compare two groups of different sizes using relative frequencies.