Reading data correctly means giving the right value with the right unit, and describing the trend in words that use the numbers. Get this step right and every later step starts from correct numbers.
This is the first lesson in body-parameter measurement concepts. The next one, interpreting repeated measurements, builds on it.
What do I check before using a number?
Check three things before you calculate or describe anything: the unit, the counting time and the scale of the axis.
A pulse count without its time is meaningless. “30 beats” could be 30 in 15 seconds or 30 in a full minute, and the rates differ by a factor of four.
Worked example: resting and after exercise
Bryan counts his pulse for 15 seconds at rest and again after 2 minutes of star jumps.
| Condition | Beats in 15 seconds | Beats per minute |
|---|---|---|
| At rest | 18 | 18 × 4 = 72 |
| After star jumps | 30 | 30 × 4 = 120 |
The question asks: describe the change in pulse rate.
Answer: the pulse rate increased from 72 to 120 beats per minute after exercise, a rise of 48 beats per minute (120 − 72 = 48).
Now read a line graph of Bryan’s temperature. The x-axis is time in minutes and the y-axis is temperature in °C. The graph shows 36.5 °C at 0 minutes, 36.9 °C at 10 minutes and 37.1 °C at 20 minutes. Write the trend as: temperature rises from 36.5 °C to 37.1 °C over 20 minutes, a total rise of 0.6 °C.
The mistake that costs marks
A student writes that the pulse rose from 18 to 30. The numbers are real, but they are counts over 15 seconds, not rates.
| Wrong | Right | |
|---|---|---|
| Values used | 18 and 30 | 72 and 120 |
| Unit | none | beats per minute |
| Change | 12 | 48 beats per minute |
Also watch graph scales. If each small square is 0.2 °C, a point one square above 36.4 °C is 36.6 °C, not 37.4 °C.
Check yourself
Amirah counts 22 beats in 15 seconds at rest and 27 beats in 15 seconds after walking. Give both rates and the increase.
Answer
Resting: 22 × 4 = 88 beats per minute. After walking: 27 × 4 = 108 beats per minute.
The increase is 108 − 88 = 20 beats per minute. Check: the difference in counts is 5, and 5 × 4 = 20.
What to study next
Once you read single values reliably, move to interpreting repeated measurements and variation. Use the graph evidence comparison lab to practise axis reading.
For a teacher to go through your data questions with you, see online one-to-one Science tuition.