ACARA v9 CONTENT DESCRIPTION “analyse data and information to describe patterns, trends and relationships and identify anomalies”
Builds on earlier work reading tables and simple graphs. Here the focus shifts from recording numbers to making sense of them: describing the overall trend in a set of results, and noticing the one reading that does not fit.
Data tells a story once you read its shape
When you repeat a measurement across changing conditions, the results often form a pattern: they rise, they fall, or they hold steady. Describing that pattern is the first job of analysis. The second job is to notice anything that breaks it. A reading that sits far from the run of the others is called an anomaly, and it is a signal worth checking rather than a number to ignore.
Find the reading that does not fit
A group cooled a beaker of water and logged its temperature each minute. The temperature should fall smoothly. Click the point where something went wrong.
Click the point that does not fit the pattern of the others.
Describe the trend before you judge a point
To know what counts as an anomaly, you first have to see the trend. A table of numbers can hide its own shape, so turning the same data into a graph makes the trend visible at a glance. Once the line of expected behaviour is clear, any point sitting well above or below it stands out.
The same results, read three ways
A student timed how long an ice cube took to melt at five room temperatures. Switch between the table, the bar chart and the line graph.
The numbers fall as the room gets warmer, but the line graph makes the trend obvious: warmer rooms melt the ice faster, and the points sit on a smooth downward curve with no reading out of place.
Describing a relationship is a claim about the data
Once a trend is clear, the next step is to put it into words. But it is easy to say more than the data shows, or to mix a real relationship up with a coincidence. A careful description states only what the numbers support, and stops there. Read each statement about the results below and decide which ones the data actually backs.
Which descriptions does the data support?
A class recorded the volume of carbon dioxide gas given off when they dropped antacid tablets into water at five temperatures. The volume rose steadily as the water got warmer. Sort each statement as a sound description of that data, or one that reaches too far.
Claim: The data shows that more carbon dioxide is released as the water gets warmer.
At each higher temperature tested, from 10 to 50 degrees, the measured volume of gas was larger than at the step before.
The volume rose by a similar amount for each ten-degree increase, so the relationship looks close to steady across the range tested.
The reaction will keep speeding up without limit, so at one hundred degrees the gas volume would simply be five times the value at fifty.
Because warmth and gas rose together, the gas being released must be what warmed the water.
Decide whether each statement is evidence for the claim, or not.
A trend can change shape as more data comes in
A relationship you describe from a few points is provisional. Extending the measurements can confirm the pattern, or reveal that it bends or levels off where you did not expect. Step through the readings below and watch how the best description of the trend is revised as each new point is added.
Watch the trend take shape, point by point
A group warmed a sealed flask of air and measured its pressure as the temperature rose. Add each reading and see how the relationship they would report changes.
New evidence (1 of 3)
At 0 and 20 degrees the pressure readings are 101 and 108 kilopascals.
Accepted model: Pressure rises as temperature rises.
Add the next piece of evidence and watch whether the accepted model holds or has to change.
Why this matters
Real measurements are never perfect. Being able to describe a trend, and to flag the single result that breaks it, is what separates raw numbers from evidence. Scientists, engineers and doctors all rely on the same skill: read the pattern, then question the point that does not belong.
Quick self-check
1. A class measures how far a toy car rolls from five ramp heights. The distances rise steadily, except one reading that is far shorter than the readings on either side. What is that short reading best called?
2. Plant heights measured each week are 2, 4, 6, 8 and 10 cm. How would you best describe this data?
3. Why is plotting numbers on a graph useful for spotting an anomaly?
4. Daily rainfall for a week is 3, 4, 3, 19, 4, 3, 4 millimetres. Which value is the anomaly?
5. After finding an anomaly in your results, what is the best next step?