Recording Data: Tables, Units & Repeats

Revise Recording Data: Tables, Units & Repeats for Biology 3 (IAL) WBI13 (AS Level) — revision notes, 2 practice questions and instant AI marking.

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Edexcel IAL Biology • Unit 3: Practical Skills in Biology I

Recording Data: Tables, Units & Repeats

📋 Big idea: A results table is marked before anything is plotted. Headings with units, a consistent number of decimal places, the independent variable on the left and the mean worked out to the right — these are marks awarded for the table itself, independent of whether the experiment worked.

Summary — What This Topic Covers

Laying out a results table that gains the presentation marks
Writing headings with units in the correct form
Why every value in a column needs the same number of decimal places
How many repeats, and what a mean does and does not fix
Recording raw data and processed data separately

1. The Anatomy of a Results Table

┌──────────────┬────────────────────────────────────┬────────────┐ │ Temperature │ Volume of oxygen / cm³ │ Mean │ │ / °C ├──────────┬──────────┬──────────────┤ volume │ │ │ Repeat 1 │ Repeat 2 │ Repeat 3 │ / cm³ │ ├──────────────┼──────────┼──────────┼──────────────┼────────────┤ │ 10 │ 4.0 │ 4.5 │ 4.0 │ 4.2 │ │ 20 │ 8.5 │ 8.0 │ 9.0 │ 8.5 │ │ 30 │ 14.0 │ 13.5 │ 14.5 │ 14.0 │ │ 40 │ 17.5 │ 18.0 │ 17.0 │ 17.5 │ └──────────────┴──────────┴──────────┴──────────────┴────────────┘

Independent variable in the leftmost column, in ascending order
Dependent variable repeats to the right, then the mean
Units in the heading only — never repeated beside every number
Every value in a column to the same number of decimal places
Ruled lines, and no empty cells

2. Headings and Units

The convention

Write the quantity, then a solidus, then the unit: Temperature / °C, Volume of oxygen / cm³, Rate / cm³ s⁻¹. The column then contains bare numbers.

✓ Time / s 45 60 75 ✗ Time 45 s 60 s 75 s ✗ Time (seconds) 45 60 75 ← acceptable, but / is preferred ✓ Rate / cm³ s⁻¹ 0.24 0.31 0.42 ✗ Rate / cm³/s ← use negative indices, not a second solidus

Common mistake

Two solidi in one unit. "cm³/s" reads as ambiguous; write cm³ s⁻¹. With one solidus already separating quantity from unit, a second one is genuinely confusing.

3. Decimal Places

The rule

Every value in a column must be recorded to the same number of decimal places, set by the resolution of the instrument — not by what the number happened to look like.

✗ 4 ✓ 4.0 4.5 4.5 4.25 4.0 ← a 0.5 cm³ syringe cannot give 4.25 A mean may be given to ONE extra decimal place, because averaging several readings justifies slightly more precision: 4.0, 4.5, 4.0 → mean 4.17 cm³

What mark schemes look for

A column reading 4, 4.5, 4.25 tells the examiner you recorded whatever the calculator gave rather than what the apparatus could measure. It costs the table mark.

4. Repeats and Means

Key Term

Repeats are measurements of the same condition, taken under identical settings. Their mean is more reliable than any single value because random errors partly cancel.

Three repeats is the normal minimum at this level; more is better
anomaly
before
range

What a mean cannot do

random

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Practice Questions
What to Memorise
Concepts Checklist
Exam Tips
5. Raw Data vs Processed Data

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