Be able to add a second data series

Topic 16 – Graphs and Charts

Objective

Create, label, edit and interpret a chart that contains a second data series in line with the Cambridge IGCSE ICT (0417) syllabus requirements.

1. When to use a second data series

• Comparing the performance of two products, services or locations over the same period.
• Showing actual versus projected/target values.
• Displaying two related variables (e.g., temperature and rainfall, revenue and profit).
• Any situation where the same categories (months, quarters, years, etc.) apply to both sets of data.

2. Chart types allowed by the syllabus

The IGCSE ICT specification only expects the following chart types. Avoid pie‑charts, radar charts, 3‑D effects or decorative styles – they are not part of the assessment.

3. Exam‑specific checklist (AO1 / AO2)

Use this checklist verbatim when you create a chart for the evidence document. The wording mirrors the syllabus.

4. Preparing the data

1. Enter the category labels in one column (e.g., Month).
2. Enter Series 1 data in the next column and Series 2 in the column after that.
3. Both series must contain the same number of rows and the categories must be ordered identically.
4. If a value is missing:

   • Leave the cell blank – the spreadsheet will treat it as “no data”.
   • Do not enter “0” unless a true zero value is intended.

5. Ensure numeric formatting is consistent (no mixed currency symbols, same number of decimal places, etc.).

5. Adding a second data series

5.1 Creating the chart with both series at once

1. Select the entire data range, including the category column and both series columns.
2. Choose Insert → Chart and pick one of the syllabus‑approved chart types.
3. The program automatically plots both series.
4. Proceed to editing the chart (titles, legend, colours, etc.).

5.2 Adding a second series to an existing chart

1. Click the chart to activate the Chart Tools ribbon.
2. Choose Design → Select Data (or “Chart → Data → Select Data”).
3. In the “Select Data Source” dialog, click Add under “Legend Entries (Series)”.
4. Enter the series name (e.g., “Product B”).
5. For Series X values, select the range of category cells (e.g., \$A\$2:\$A\$7).
   

   For Series Y values, select the range of the second data column (e.g., \$C\$2:\$C\$7).

6. Click OK → OK again to close the dialog. The new series appears on the chart.

5.3 Editing and formatting the chart (AO2)

• Chart title: Click the placeholder and type a meaningful title (e.g., “Monthly Sales – Product A & B”).
• Axis titles: Use Chart Elements → Axis Titles or right‑click the axis → “Add Axis Title”.
• Legend: Move it to a clear corner; edit the default text (“Series 1”, “Series 2”) to something descriptive.
• Series formatting:

  • Assign contrasting colours (e.g., blue for Series 1, red for Series 2).
  • For line charts, use different line styles (solid vs. dashed) or distinct markers (circle, square).

• Data labels (optional): Right‑click a series → “Add Data Labels”. Use them only if space permits; they are not required by the syllabus.
• Gridlines & scaling:

  • Keep major gridlines light grey; remove minor gridlines.
  • Set the Y‑axis minimum to 0 unless a justified reason exists; choose an appropriate maximum so the data fill most of the plot area.

• Secondary Y‑axis (only when ranges differ markedly):

  • Right‑click the series that needs a different scale → “Format Data Series” → “Plot Series on Secondary Axis”.
  • Add a secondary axis title and ensure the primary and secondary axes are clearly distinguished.

• Plot area: Drag the edges of the plot area so that axis titles and legends do not overlap the data.
• Chart size: Resize the whole chart so its width ≤ 15 cm (or the centre’s specification).
• Export / insert: Copy the chart → paste as picture, or use “Save as picture” (PNG recommended) and insert the image into the evidence document.

6. Mini‑example – Column chart with two series

Data set: quarterly visitor numbers for two museums.

Key points to notice:

• When “Column” is chosen, the “Add Series” dialog is identical to the line‑chart process, but the visual result shows two bars side‑by‑side for each quarter.
• Because the visitor numbers have similar ranges, a secondary Y‑axis is unnecessary.
• Adding data labels to each column can make the exact values instantly visible – optional but useful for the exam.

7. Practice exercise (full IGCSE style – AO1, AO2, AO3)

Create a column chart using the data below. Follow the exam‑specific checklist (section 3) and the step‑by‑step guide (section 5). Insert the chart as a picture into your evidence document and then answer the questions.

1. Which museum had the greatest increase in visitors from Q1 to Q4?
2. What is the total number of visitors for each museum over the year?
3. Describe one visual difference you notice between the two series on the chart (e.g., height of columns, colour contrast, spacing).
4. Interpret the trend: What does the chart suggest about the relative popularity of the two museums over the year? (This tests AO3 – analysis/evaluation.)

8. Summary of key points

• Prepare data correctly: identical categories, equal row count, consistent numeric formatting.
• Choose only the syllabus‑approved chart types (line, column/bar, area, scatter).
• Use the “Add Series” function to plot a second data series; then edit titles, legends, colours, gridlines, scaling and size to meet the exam checklist.
• Start the Y‑axis at 0 unless you can justify a different start; use a secondary Y‑axis only when the series ranges differ markedly.
• Keep the chart width ≤ 15 cm, avoid 3‑D effects, and insert the final chart as a PNG/JPEG picture.
• Finally, always interpret the chart: compare trends, comment on notable differences and answer the AO3 questions – this demonstrates the analytical skills required in the IGCSE exam.