Year 8 Science · Unit 4 · Lesson 5
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Learning Goals
Find the mistake
A student's graph choice
"I investigated the germination rates of five different plant species (Grevillea, Wattle, Banksia, Kangaroo Paw, and Bottlebrush) after two weeks in identical conditions. I drew a line graph with the five species along the x-axis and germination rate (%) on the y-axis. I connected all five points with a single line."
(a) Why is a line graph the wrong choice for this investigation? Be specific about the type of data on the x-axis.
(b) What graph type should be used? Explain why it is more appropriate.
(c) List four features the correctly drawn graph must include.
Choose and justify
Two investigations — two different decisions
Investigation 1: A student measures heart rate (beats per minute) every 2 minutes during 20 minutes of exercise, then every 2 minutes for 10 minutes of recovery.
Investigation 2: A student measures the average height (cm) of bean plants grown with four different fertiliser types (Osmocote, Seasol, Powerfeed, no fertiliser) after 4 weeks.
For each investigation, complete the three response boxes.
| Question | Investigation 1: Heart rate over time | Investigation 2: Fertiliser type vs plant height |
|---|---|---|
| Best graph type | ||
| Justify your choice — why does this graph type suit this data? | ||
| List 4 required features for your graph |
1. Why does connecting categorical data points with a line give a misleading impression to the reader?
2. A student wants to show that 78% of air is nitrogen, 21% is oxygen, and 1% is other gases. Identify the best graph type and explain why it suits this data.
Wrap Up
In one sentence, what was the main idea of this lesson?