How_To_Be_Good_At_Math

STATISTICS • VENN DIAGRAMS 275

Art class

Let’s join the music and soccer

sets together so that their

circles overlap. When we join two

sets, it’s called a union of sets.

We’ve now made a Venn diagram.

An overlap between two sets is

an intersection. It shows when

something belongs to more than

one set. This intersection shows that

Rona and Steve do both activities.

Now let’s join the art set to the

other two sets, so that all three

sets overlap. If we look at the

intersections, we can see which

friends do more than one activity.

Our three-set Venn diagram

includes only seven of the

eight friends. Owen doesn’t do any

after-school activities, so he doesn’t

belong to any of those sets.

Steve

does every

activity

Intersection

(overlap)

Rona does

football

and music

Rona and

Steve belong

to both sets

Sarah does

art and music

Tessa does art

and football

Owen does

no activities

Owen

Steve

Tessa

Tessa

Mabel

Mabel

Music lesson Football practice

To show the universal set, we

draw a box around all the

intersecting circles in our diagram.

The box must include Owen.

Even though he is not in any of

the after-school activity sets, he is

still part of the group being sorted.

The universal set

The universal set is the set that

contains everybody or everything

that is being sorted, including

those not in the overlapping sets.

Shahid

Rona

Peter

Sarah Tessa

Music lesson Football practice

Steve

Steve

Shahid

Shahid

Rona

Rona

Peter

Peter

Sarah

Sarah

Art class

Music lesson Football practice

Owen

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