← VCE Spreadsheets, SQL & Visualisation

Adding a trendline to a chart

A straight or curved line fitted to the points on a chart. It shows the overall direction of the data, such as going up or down. Add it with Add Chart Element > Trendline.

Part of: VCE Applied Computing - U1O1 - Data analysis — Module 66, 7-8 Digital Technologies: Analysing and visualising data — Module 24, ACARA Digital Technologies Years 7–8 — Analysing and Visualising Data — Module 47

Understanding Adding a trendline to a chart in VCE Spreadsheets, SQL & Visualisation

What it does: A linear trendline is a straight line fitted to the points. It is added from the Add Chart Element menu. A line that starts high and ends low shows the data is generally decreasing, such as phone battery level through the day. A line rising to the right means the values are generally getting bigger over time. A trendline is a best fit for the overall pattern. Points above or below it just show variation in the data. Trendlines work with number data plotted on a chart. Names alone have no direction to show. A point far from the pattern is an outlier. The trendline helps you spot it.

Common mistakes: A trendline is not a chart type. First insert a chart such as Scatter (Insert > Chart > Scatter), then add the trendline to it. Gridlines are only background lines. To show the overall direction you need Add Chart Element > Trendline.

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This module's key terms are also in a printable crossword (Modules 55–70) and word search (Modules 55–86).

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Learning
Duo
What does a trendline show on a chart?
The overall direction of the dataThe exact value of every single point
Matches
Point far above the trendline = the trendline is wrong
↓
Points above or below the line do not mean the trendline is wrong. The trendline shows the overall direction, so some points will sit above it and some below it.
Applying
Meanings
Term
Trendline
Meaning
A straight or curved line fitted to the points on a chart. It shows the overall direction of the data, such as going up or down. Add it with Add Chart Element > Trendline.
Practice
Click the chart
Testing
Gaps
Add Chart Element >
Check Answer
Spots
1Select cells A1:B8
2Insert > Chart > Trendline

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Quick Questions

1. What does a trendline show on a chart?
A. The overall direction of the data ✓
B. The exact value of every single point
A trendline is fitted to the points to show the general direction, such as going up or down.
2. Which menu path adds a trendline in a spreadsheet chart?
A. Format Cells > Trendline
B. Add Chart Element > Trendline ✓
Click your chart, then choose Add Chart Element > Trendline. Format Cells changes how numbers look in cells.
3. A trendline slopes up from left to right. What does this tell you?
A. The data is trending upward ✓
B. The data is trending downward
A line rising to the right means the values are generally getting bigger over time.
4. A student charts the temperature each day as winter begins. The trendline slopes down to the right. What is the trend?
A. Temperatures are generally falling ✓
B. Temperatures are generally rising
A line sloping down to the right shows a downward trend, so values are getting smaller.
5. Which statement about a trendline is true?
A. Every point must sit exactly on the line
B. Some points can sit above or below the line ✓
A trendline is a best fit for the overall pattern. Points above or below it just show variation in the data.

Match the Pairs

Add Chart Element > Trendline → The menu steps that add a trendline to a chart so you can see the overall direction of the data
Trendline sloping upward → An upward trend: the values are mostly going up over time
To show the overall direction of your chart points, you add a line fitted to them → Chart Design > Add Chart Element > Trendline > Linear
A downward trend means the trendline slopes down from left to right → Trendline: high on the left, low on the right
Point far above the trendline = the trendline is wrong → Points above or below the line do not mean the trendline is wrong. The trendline shows the overall direction, so some points will sit above it and some below it.
Select a cell > Insert > Trendline (without a chart) → A trendline can only be added to a chart. You must create the chart first, then use Add Chart Element > Trendline.

Key Term

Trendline
A straight or curved line fitted to the points on a chart. It shows the overall direction of the data, such as going up or down. Add it with Add Chart Element > Trendline.

Fill in the Blanks

1. Add Chart Element > Trendline
Hint: Type the menu item that draws a fitted line through the chart points.
2. Add Chart Element > Trendline
Hint: Type the name of the chart menu you open first to add extras like a trendline.
3. Slope above 0 means an upward trend
Hint: Type the direction word for a line that rises from left to right.
4. Point above line = higher than the trend
Hint: Type the comparison word for a point sitting above the trendline.
5. Straight line trendline type: Linear
Hint: Type the trendline type that gives a straight line.

Spot the Error

Question 1
A Select cells A1:B8
B Insert > Chart > Trendline
C Add Chart Element > Trendline
Line B — A trendline is not a chart type. First insert a chart such as Scatter (Insert > Chart > Scatter), then add the trendline to it.
Question 2
A Select the data
B Insert a line chart
C Click the chart
D Add Chart Element > Gridlines
Line D — Gridlines are only background lines. To show the overall direction you need Add Chart Element > Trendline.
Question 3
A Sales: 2, 4, 6, 8, 10
B Add a trendline
C Line slopes up
D Trend: downward
Line D — The sales values keep rising and the line slopes up, so the trend is upward, not downward.
Question 4
A Data: 1, 3, 5, 7, 9
B Add a trendline
C Line slopes down
D Trend: downward
Line A — The values rise here, but the other lines say the trendline slopes down. The data should fall: 9, 7, 5, 3, 1.
Question 5
A A trendline shows each value
B Up slope = values rising
C Down slope = values falling
Line A — A trendline shows the overall direction of the data, not each exact value. It should say it shows direction.

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