Picture Graphs and Dot Plots

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What this lesson covers

  • A data picture shows how many answers are in each category.
  • Picture graphs and dot plots are kinds of data pictures.
  • In a dot plot, every dot is the same size and stands for one answer.
  • A graph helps tell the story of the data.
Key idea

Graphs tell a story

  • A list of answers is hard to read.
  • A graph shows how many answers are in each category. That number is the frequency.
  • One look tells you which category has the most.
Key idea

Picture graphs

  • In a picture graph, one picture stands for one answer.
  • Line the pictures up in rows, all the same size and evenly spaced.
Favourite fruitPicture graphFrequency
apple● ● ● ● ●5
banana● ● ●3
kiwifruit● ● ● ● ● ●6
orange● ●2
Key idea

Try it: change the counts

Key idea

Dot plots

  • A dot plot uses a dot for each answer.
  • Every dot is the same size, and the dots are stacked evenly.
  • So the tallest stack is the category with the most.
Worked example

Make a dot plot

  • Room 4 asked: How do students in Room 4 get to school?
  • One dot for each student, stacked above their category.
Way to schoolDotsFrequency
walk● ● ● ● ●5
car● ● ● ● ● ● ●7
bus● ● ●3
bike● ● ● ●4
Key idea

Try it: graph the way to school

Worked example

Say what it shows

  • Name the variable and who was asked: how students in Room 4 get to school.
  • Give each frequency: 5 walk, 7 come by car, 3 take the bus and 4 bike.
  • Say the most and the least: car is the most common and bus is the least.

Common mistakes

  • Drawing some dots bigger than others.
    Every dot must be the same size, or the graph tricks the eye.
  • Saying "car is 7" with nothing else.
    Name the variable and context: 7 students in Room 4 come to school by car.
  • The category on the left has the most.
    Order does not matter. The tallest stack has the most.

Your turn

1

Use the Room 4 dot plot. How many students walk?

2

Which way to school is the most common?

3

Which way to school is the least common?

4

How many more students come by car than by bus?

5

How many students are in the dot plot altogether?

Show answer

1. 5 2. car 3. bus 4. 4 5. 19

Summary

What to take away

  • A graph shows the frequency of each category.
  • One picture or dot for each answer, all the same size.
  • Name the variable and the context.
  • The tallest stack is the most; the shortest is the least.
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More in Statistics

Collecting Data and Making Tally ChartsNotesPicture Graphs and Dot PlotsNotes

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