Pearson Edexcel · GCSE · Biology
Course version: 1BI0 · Version from Sept 2016
Demonstrate an understanding of the use of percentiles charts to monitor…
Full specification wording
Topic 2 – Cells and control: 2.7 Demonstrate an understanding of the use of percentiles charts to monitor growth
A percentile chart plots a measurement such as mass or length against age, with curved lines marking the values below which a given percentage of children fall.
Checked against the Pearson Edexcel 1BI0 specification (opens in a new tab) on .
- Point 7 of 16
Study notes
From the checked teaching notes for this specification point.
The idea
A percentile chart plots a measurement such as mass or length against age, with curved lines marking the values below which a given percentage of children fall. The 50th percentile is the median; the 25th and 75th percentiles bracket the middle half of children. A single plotted point shows how a child compares with others of the same age, but the real value comes from the trend: a child tracking steadily along one percentile line is growing normally, even if that line is low. A child whose plotted points cross downwards through successive percentile lines, or whose growth flattens, may need medical review. In MCQ items, judge the pattern of several points over time rather than one reading, and read the percentile value from the correct axis and line.
What earns the marks
- A percentile chart shows the proportion of children of a given age who fall below a particular measurement, so the 50th percentile is the median value.
- A single point compares a child's measurement with others of the same age, but monitoring growth requires repeated measurements plotted over time.
- Steady tracking along one percentile line indicates normal growth, even if the child is on a low percentile such as the 10th.
- Crossing downwards through percentile lines, or a flattening curve, can indicate a growth problem and may prompt further investigation.
- Correct use requires reading the value from the appropriate axis and identifying the percentile line, then interpreting the trend across several points.
Common mistakes and how to put them right
Judging a child as abnormal just because a single point is on a low percentile.
Put it right: The trend over time matters more than one reading.
Thinking the 50th percentile is a target every child should reach.
Put it right: It is the median, and healthy children lie on many different lines.
Reading the percentile number as a percentage of expected growth.
Put it right: It is the percentage of children below that measurement at that age.
Exam tips
- Look at the direction of travel across several plotted points before deciding whether growth is normal.
- Check which axis carries age and which carries the measurement before reading any value.
- When an option mentions a single point, ask whether the question is about comparison at one age or monitoring over time.
Try the lesson
The start of the Topic 2 – Cells and control: 2.7 Demonstrate an understanding of the use of percentiles charts to monitor growth lesson, made from checked teaching notes for this specification point.
Have a go first
On a growth percentile chart, what does it mean if a child's mass is on the 50th percentile line?
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