Reading Bar Graphs and Line Plots

What Are Graphs?

Graphs are visual ways to show data (information).

They help us:

• See patterns quickly
• Compare information
• Answer questions about data
• Make the data easier to understand

Bar Graphs

Bar graphs use bars (rectangles) to show data.

Parts of a bar graph:

• Title: Tells what the graph is about
• Labels: Names on the bottom (categories)
• Scale: Numbers on the side (how much)
• Bars: Show the amount for each category

Reading a Bar Graph

Example: Favorite Fruits

        Number of Students
        |
    10  |     ▓▓▓
     9  |     ▓▓▓
     8  |     ▓▓▓  ▓▓▓
     7  | ▓▓▓ ▓▓▓  ▓▓▓
     6  | ▓▓▓ ▓▓▓  ▓▓▓
     5  | ▓▓▓ ▓▓▓  ▓▓▓  ▓▓▓
     4  | ▓▓▓ ▓▓▓  ▓▓▓  ▓▓▓
     3  | ▓▓▓ ▓▓▓  ▓▓▓  ▓▓▓
     2  | ▓▓▓ ▓▓▓  ▓▓▓  ▓▓▓
     1  | ▓▓▓ ▓▓▓  ▓▓▓  ▓▓▓
     0  |_________________________
          Apple Banana Orange Grape

Reading the graph:

• Apple: 7 students
• Banana: 10 students
• Orange: 8 students
• Grape: 5 students

Questions you can answer:

1. Which fruit is most popular? Banana (tallest bar)
2. Which fruit is least popular? Grape (shortest bar)
3. How many chose apples? 7 students
4. How many more chose bananas than grapes? 10 - 5 = 5 more

Types of Bar Graphs

Vertical bar graph:

• Bars go up and down
• Categories on bottom
• Numbers on the side

Horizontal bar graph:

• Bars go left to right
• Categories on the side
• Numbers on the bottom

Both show the same information, just turned sideways!

Comparing Data in Bar Graphs

Example questions:

1. Which category has the most?

• Look for the tallest (or longest) bar

2. Which category has the least?

• Look for the shortest bar

3. How many more/fewer?

• Subtract the two amounts
• Example: 10 - 7 = 3 more

4. What is the total?

• Add all the amounts
• Example: 7 + 10 + 8 + 5 = 30 total

Reading the Scale

Important: Always check the scale!

Scale by 1s:

0, 1, 2, 3, 4, 5...
Each line = 1

Scale by 2s:

0, 2, 4, 6, 8, 10...
Each line = 2

Scale by 5s:

0, 5, 10, 15, 20...
Each line = 5

Scale by 10s:

0, 10, 20, 30, 40...
Each line = 10

Line Plots (Dot Plots)

Line plots use Xs or dots to show data on a number line.

Parts of a line plot:

• Title: What the data shows
• Number line: Shows possible values
• Xs or dots: Each one represents one piece of data

Reading a Line Plot

Example: Hours of TV Watched This Week

        X
        X          X
    X   X      X   X
    X   X   X  X   X
    X   X   X  X   X   X
   ─┼───┼───┼──┼───┼───┼──
    3   4   5  6   7   8
         Hours

Reading the line plot:

• 3 hours: 1 student (1 X)
• 4 hours: 4 students (4 Xs)
• 5 hours: 2 students (2 Xs)
• 6 hours: 4 students (4 Xs)
• 7 hours: 5 students (5 Xs)
• 8 hours: 1 student (1 X)

Total students: Count all the Xs = 17 students ✓

Answering Questions from Line Plots

Questions:

1. How many students watched 4 hours?

• Count Xs above 4: 4 students ✓

2. What was the most common amount?

• Find the tallest stack: 7 hours (5 Xs)

3. What is the range?

• Highest - Lowest = 8 - 3 = 5 hours ✓

4. How many students total?

• Count ALL Xs: 17 students ✓

Line Plots with Fractions

Line plots can show fractional data too!

Example: Length of Pencils (in inches)

        X
        X   X
    X   X   X       X
    X   X   X   X   X
   ─┼───┼───┼───┼───┼──
    5   5¼  5½  5¾  6
       Inches

Reading:

• 5 inches: 1 pencil
• 5¼ inches: 3 pencils
• 5½ inches: 3 pencils
• 5¾ inches: 1 pencil
• 6 inches: 2 pencils

Finding the Mode (Most Common)

Mode = the value that appears most often

In a bar graph:

• Find the tallest bar
• That category is the mode

In a line plot:

• Find the number with the most Xs
• That number is the mode

Real-World Examples

Bar Graph Uses:

• Favorite colors in the class
• Pets owned by students
• Books read each month
• Sales at a lemonade stand

Line Plot Uses:

• Test scores
• Heights or weights
• Temperatures over time
• Distances jumped in PE

Creating Data from Graphs

From this line plot:

    X
    X   X
    X   X   X
   ─┼───┼───┼──
    2   3   4

The data is: 2, 2, 3, 3, 3, 4

Interpreting Data

Good questions to ask:

1. What does the graph show? (Read the title!)
2. What do the numbers mean? (Check the scale!)
3. What patterns do you see?
4. What can you conclude from the data?

Comparing Two Graphs

Sometimes you need to compare graphs:

Bar Graph A: Pet Survey - Class 1 Bar Graph B: Pet Survey - Class 2

You can compare:

• Which class has more dogs?
• Which pet is most popular in both?
• What's the total for each class?

Common Mistakes

❌ Not reading the scale carefully

• Each line might be 2, 5, or 10 (not always 1!)

❌ Counting bars instead of reading values

• The HEIGHT of the bar matters, not how many bars

❌ Forgetting to read the title/labels

• You need to know what the data represents!

❌ Estimating when you should be exact

• If the bar is between lines, estimate carefully

✅ Always check the scale first ✅ Read all labels and the title ✅ Count Xs carefully in line plots ✅ Show your work when calculating

Practice Strategy

When reading any graph:

Step 1: Read the title

• What is this graph about?

Step 2: Check the labels

• What do the bottom/side show?

Step 3: Look at the scale

• Count by 1s, 2s, 5s, or 10s?

Step 4: Find the data you need

• Which bar or which stack of Xs?

Step 5: Answer the question

• Compare, add, subtract as needed

Key Vocabulary

Bar Graph:

• Bar: The rectangle showing data
• Scale: The numbers on the side/bottom
• Category: The groups being compared

Line Plot:

• X (or dot): Each mark of data
• Number line: The line with numbers
• Cluster: Where most Xs are grouped

Tips for Success

Bar Graphs:

• Use a ruler to line up the top of the bar with the scale
• If between two numbers, estimate halfway
• Taller bar = more, shorter bar = less

Line Plots:

• Count Xs carefully (easy to miss one!)
• Each X = 1 piece of data
• Stack = how many with that value

Both:

• Always start by reading the title
• Check what the numbers represent
• Show your work for calculations
• Ask: Does my answer make sense?

Summary

Bar Graphs:

• Show data with bars
• Good for comparing categories
• Read the scale carefully!

Line Plots:

• Show data with Xs on a number line
• Each X = one data point
• Good for seeing clusters and gaps

Both types help us:

• Visualize information
• See patterns
• Compare data
• Answer questions quickly

Remember: The graph is only as good as how well you read it! Always check titles, labels, and scales first! ✓