L3 · Dot plots with one-to-one correspondence

Learning goal

“I can build and read a dot plot: I put one dot above a number for each answer with that value, and each dot stands for exactly one student.”

Dot plot — a graph with a number line. One dot is placed above a number for each answer with that value.

Value — the number an answer has, like 0, 1, 2 or 3 pets.

Stack — the dots piled above one number. The stack's height is how many answers have that value.

One-to-one correspondence — each dot matches exactly one answer. One dot, one student - never more, never less.

Worked example

Our class asks: "How many pets does each student have?" Ten students answer, in this order: 0, 1, 1, 2, 0, 1, 3, 1, 2, 1. Step 1: Draw a number line with 0, 1, 2, 3. Step 2: Place one dot for EACH answer, above its value. Count the answers for each value: 0 appears 2 times, 1 appears 5 times, 2 appears 2 times, 3 appears 1 time. Step 3: The finished dot plot has stacks: above 0 - 2 dots; above 1 - 5 dots; above 2 - 2 dots; above 3 - 1 dot. Step 4: Check. Total dots: 2 + 5 + 2 + 1 = 10 - one for each of the 10 students. Say it plainly: one answer, one dot. If the dots do not total the number of students, a dot is missing or doubled.

Check yourself — explain it

Why does the value 1 get five dots?

Paired problem — example still visible

Three more students answer: 2, 0, 1. Where does each new dot go? -> Above 2, above 0, and above 1 - one dot per answer, above its own value

Faded completion — last step is yours

"In a dot plot, each dot stands for exactly ___ answer. This is called ___ correspondence." -> one; one-to-one

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