Line Graphs
Line graphs display data trends over time by connecting plotted points with line segments in Grade 8 math (Yoshiwara Core Math). The horizontal axis typically shows the independent variable (time); the vertical axis shows the dependent variable (e.g., temperature). Slope of each segment shows rate of change: steep = fast change; flat = no change; downward = decrease. Line graphs enable interpolation (estimating between data points) and comparison of multiple data sets. They are the key tool for data literacy in Grade 8 statistics.
Key Concepts
Property Graphs are especially useful for illustrating the relationship between two variables. We could instead place a dot at the top of each bar. If we connect the dots with line segments, we have created a line graph. We often use line graphs to illustrate trends in data over time.
Examples A line graph shows a student's test scores over a semester: 85 in September, 88 in October, 92 in November, and 90 in December. The line connecting these points shows a general improvement.
A line graph tracks the daily temperature for a week. The points might be $15^\circ C$, $17^\circ C$, $16^\circ C$, $19^\circ C$, $20^\circ C$, $18^\circ C$, and $17^\circ C$. The line shows the temperature fluctuations.
Common Questions
What type of data suits a line graph?
Data changing continuously over time — temperature, population, stock prices. Use when the trend between points matters.
How do you read rate of change from a line graph?
Steeper segments = faster rate of change. Flat = no change. Downward slope = decrease.
What is interpolation on a line graph?
Estimating a value between two known data points using the connecting line.
How do you construct a line graph?
Label axes with variables and units, choose a scale, plot data points, connect consecutive points with straight segments.
How is a line graph different from a scatter plot?
A line graph connects consecutive data points to show trends; a scatter plot shows individual distribution without connecting lines.