Types of Graphs
| Graph type | Best for |
|---|---|
| Bar chart | Comparing categories |
| Line graph | Showing change over time |
| Pie chart | Showing parts of a whole |
| Pictogram | Simple frequency data |
Reading a Bar Chart
Averages
Mean
Median
The middle value when data is sorted in order. (Average of two middle values if even count.)
Mode
The value that appears most often.
Dataset: 4, 7, 2, 9, 7, 3, 7
Sort: 2, 3, 4, 7, 7, 7, 9
Mean
Median = 7 (middle value of 7 numbers)
Mode = 7 (appears 3 times)
Line Graphs
Line graphs show trends over time. Join plotted points with straight lines.
A steep line means rapid change; a flat line means little change.
Real world: sports league table
A football league records goals scored per match over a season: 1, 3, 2, 0, 4, 2, 2, 3, 1, 2. Mean ; Mode = 2; Median = 2. A bar chart of these results instantly shows that 2-goal games are most common â useful data for analysts and commentators.
Real world: weather temperature trend
A meteorologist plots daily high temperatures over a week on a line graph. A steep upward slope MondayâWednesday shows rapid warming; a flat section ThursdayâFriday shows stable conditions. Line graphs make temperature trends immediately visible for public forecasts.
Real world: election results
After a school council vote (80 students total), results are: Class A 32, Class B 24, Class C 16, Class D 8. A bar chart comparing these four values lets students see at a glance which class had the highest turnout.
Practice Problems
Find the mean, median, and mode of: 5, 8, 3, 8, 6
Show answer
A bar chart shows book sales: Mon 40, Tue 25, Wed 55, Thu 30. What is the mean daily sales?