Be able to select data to produce a graph or chart including using contiguous data, non-contiguous data and specified data ranges

Published by Patrick Mutisya · 14 days ago

IGCSE ICT 0417 – Topic 16: Graphs and Charts

Topic 16 – Graphs and Charts

Learning Objective

Be able to select data to produce a graph or chart, including using contiguous data, non‑contiguous data and specified data ranges.

1. Why use graphs and charts?

Graphs and charts transform raw numerical information into a visual form that can be quickly interpreted. They are essential for:

  • Comparing quantities

  • Showing trends over time

  • Illustrating relationships between variables

  • Communicating findings to a non‑technical audience

2. Common types of graphs and charts

Chart TypeTypical UseBest Data Structure
Bar chartComparing discrete categoriesNon‑contiguous categorical data
Column chartSame as bar chart but vertical; often used for time‑based dataContiguous or non‑contiguous data
Line graphShowing trends over a continuous interval (e.g., months, years)Contiguous numerical data
Pie chartDisplaying parts of a whole (percentages)Limited number of categories (usually ≤ 6)
Scatter plotInvestigating relationship between two variablesPairs of numerical data (x, y)

3. Selecting the appropriate data

Before creating a graph you must decide which data to include. Consider the following questions:

  1. What is the purpose of the graph? (compare, show trend, illustrate proportion)

  2. Which variables are relevant?

  3. Is the data set contiguous (all values in a continuous range) or non‑contiguous (selected separate points)?

  4. Do I need to limit the range (e.g., only the first 12 months)?

4. Contiguous vs. non‑contiguous data

Contiguous data are values that follow one another without gaps. Example: monthly sales for January–December.

Non‑contiguous data are selected values that are not adjacent in the original list. Example: sales for January, March, July and October.

When using spreadsheet software, you can select non‑contiguous cells by holding Ctrl (Windows) or Command (Mac) while clicking the required cells.

5. Specified data ranges

Sometimes you need only a portion of a larger data set. This is called a specified data range. Typical reasons include:

  • Focusing on a particular period (e.g., Q1 only)

  • Excluding outliers that would distort the visual scale

  • Comparing two distinct intervals side‑by‑side

In a spreadsheet you can define a range using cell references, e.g., A2:A13 for the first twelve rows.

6. Step‑by‑step process to create a graph

StepActionKey Considerations
1Identify the purpose of the graph.Choose the chart type that best matches the purpose.
2Collect the data set.Ensure data are accurate and complete.
3Select the required cells.Use contiguous selection for continuous data, or hold Ctrl/Command for non‑contiguous cells.
4Insert the chart via the software’s “Insert → Chart” menu.Check that the software has correctly interpreted the axes.
5Adjust the data range if necessary.Modify the range in the chart data source dialog.
6Label axes, add a title, and include a legend.Use clear, concise labels; avoid abbreviations that are not explained.
7Review the graph for accuracy and readability.Check scale, data points, and that the graph answers the original question.

7. Example scenarios

  1. Scenario A – Monthly temperature trend

    Data: Average temperature for each month (January–December).

    Required graph: Line graph using contiguous data \$n = 12\$.

    Suggested diagram: Line graph showing a smooth curve from January to December.

  2. Scenario B – Sales of four products

    Data: Sales figures for Product A, C, and E only (non‑contiguous columns).

    Required graph: Bar chart with non‑contiguous data selection.

    Suggested diagram: Vertical bar chart with three separate bars labelled A, C, E.

  3. Scenario C – Exam scores for the top 5 students

    Data: Full class list of 30 scores; only the highest five are needed.

    Required graph: Column chart using a specified data range (top‑5 values).

    Suggested diagram: Column chart displaying five columns, each representing a top score.

8. Common pitfalls and how to avoid them

  • Choosing the wrong chart type – match chart type to data purpose.

  • Including too many categories in a pie chart – limit to 5‑6 slices for clarity.

  • Using non‑contiguous data without proper selection – verify that all intended cells are highlighted.

  • Incorrect axis scaling – ensure the axis starts at zero for bar/column charts unless a truncated scale is justified.

  • Missing labels or legends – always provide a clear title, axis labels, and a legend when more than one data series is plotted.

9. Summary checklist

  1. Define the purpose of the graph.

  2. Select the appropriate chart type.

  3. Determine whether the data are contiguous, non‑contiguous, or a specified range.

  4. Gather and verify the data.

  5. Use the correct selection method (continuous drag or Ctrl/Command click).

  6. Insert the chart and adjust the data range if needed.

  7. Add titles, axis labels, and a legend.

  8. Review for accuracy, readability, and relevance to the original question.