Thinking and Working Scientifically & Laboratory Reference
TWS 3: Collecting and Recording Data — Tables, Repeat Readings & Anomalies
5 min read 6 parts Lesson 3 of 8
Lesson summary
TWS 3: Collecting and Recording Data — Tables, Repeat Readings & Anomalies — Alhussan International Academy — Science (Stages 7–9) notes: Record results in a well-designed table with correct units, calculate a mean from repeat readings and identify and treat anomalous results.Lay…
- Control variables
- Calculated values
- Observations
- Evaluation
- Random error
- Results table
Part 1 of 6Designing a results table
- Layout — measurements are easier to understand in a clear table, drawn before the experiment.
- The name of the variable you change or compare goes in box X, with its units if measurable.
- The name of the variable you observe or measure goes in box Y, with its units.
- One line is used for each test planned.
- Control variables — write the controlled variables and their values under the table, for example volume of water = 50 cm3.
- Calculated values — when quantities are calculated from measurements, add another column for them.
- Observations — adapt the table, with boxes large enough for images or diagrams if needed.
Part 2 of 6Using the correct units
- Wrong units give wrong calculations.
| Quantity | Units |
|---|---|
| Temperature | degrees Celsius (°C) |
| Time | seconds (s), minutes (min), hours (h) |
| Volume | cubic centimetres (cm3), cubic decimetres (dm3) |
| Mass | grams (g), kilograms (kg), tonnes (t) |
| Length | millimetres (mm), centimetres (cm), metres (m), kilometres (km) |
- Placement — units go in the column heading and not in every cell.
Part 3 of 6Repeat measurements
- Repeatsin most fair tests the dependent variable is found more than once, usually three times.
- Recordingall repeats go in the table, always to the same number of decimal places.
- Columnsdraw boxes for each repeat result and an average.
Part 4 of 6Anomalous results
1Anomalous result1 point
= a result that does not fit the pattern and is very different from the others.
- It is often caused by a random error such as misreading a scale or starting a stopwatch late.
2Checking2 points
— do not erase it.
- Repeat the measurement, and if one is very different from the other two, put a line through it and ignore it.
- Use the new measurement instead.
3Reason
— look for why it happened, such as a messy method or a missing ruler, and leave it out of the mean if the cause is found.
Part 5 of 6Calculating the mean
- Mean the sum of all the repeats divided by the number of repeats.
- Timingcalculate it only when you are confident there are no anomalous results.
- Roundingthe average is rounded to the same number of decimal places as the data.
- Effectrepeating and averaging reduces the effect of random errors and makes the data more reliable.
Part 6 of 6Why the table matters
- Graphsa clear table makes plotting easy, with the independent variable on the x-axis and the mean dependent variable on the y-axis.
- Evaluationanomalies kept visible (crossed out, not erased) can be commented on later.
- Precisionconsistent decimal places show the precision of the instrument.
Last updated: