Statistics and Data - Interpreting and constructing line graphs

Grade 4IGCSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Definition: A line graph uses points connected by line segments to show how data changes, usually over a period of time.

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Axes: The horizontal axis (x-axis) usually represents time (days, months, hours), and the vertical axis (y-axis) represents the quantity being measured.

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Scale: Choosing an appropriate scale for the y-axis so all data points fit and are easy to read (e.g., counting by 2s, 5s, or 10s).

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Plotting: Each data point is represented by a coordinate (Time, Value).

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Trends: An upward slope indicates an increase, a downward slope indicates a decrease, and a horizontal line indicates no change.

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Interpreting: Reading specific values from the graph by looking at where a point aligns with the x and y axes.

📐Formulae

\text{Interval Size} = \frac{\text{Highest Value}}{\text{Number of Grid Lines}}

\text{Difference in Value} = \text{Value at Time 2} - \text{Value at Time 1}

\text{Trend} = \text{Direction of the line (Upward/Downward/Flat)}

💡Examples

Problem 1:

18^{\circ}C

Solution:

24^{\circ}C - 18^{\circ}C = 6^{\circ}C

Explanation:

To find the increase, identify the values on the y-axis for both time points on the x-axis and subtract the earlier value from the later value.

Problem 2:

On a graph tracking a seedling's height, the points are: Day 1 (2cm), Day 2 (4cm), Day 3 (6cm). If the trend continues, what will the height be on Day 5?

Solution:

10cm

Explanation:

6 + 2 = 8cm

Problem 3:

If the y-axis of a graph starts at 0 and has 5 equal intervals reaching up to 50, what is the value of each grid line?

Solution:

10 units per line

Explanation:

50 \div 5 = 10