IB DP Physics skill pack: uncertainties on a graph, SL and HL (first assessment 2025). Uncertainty bars, extreme lines, gradient and intercept uncertainty, and linearizing: the four moves a Paper 1B analysis is marked on.

What this pack is, and what it is not
The IB guide asks for these techniques to be practised inside the topics and the investigations that need them, so this is not a taught unit of the course and does not claim to be one. It is reference and remedial material for a technique practical physics assumes: it supplements integrated teaching rather than replacing it. It earns its place before a class meets uncertainty on a graph, and again as revision before the internal assessment and Paper 1B.

This pack is worked, not taught: the 200 minutes quoted is student working time across the practice bank, not classroom delivery time. It runs as five sittings, 31 to 50 minutes each, marked on the page.

Where this pack starts
It assumes the arithmetic of uncertainty rather than teaching it: the rules at the head of the pack restate exactly as much of it as the graph work needs, so it can be worked with nothing else to hand. A companion skill pack covers recording and propagation in full. What this pack owns is what uncertainty does to a graph once the readings are in front of you.

What students learn

• The uncertainty that becomes a bar.
• The line of best fit, and the two extreme lines.
• A gradient, an intercept, and the uncertainty in each.
• Linearizing where it is appropriate, and the intercept read as a diagnostic.

IB skills this pack teaches and practises

• Drawing and interpreting uncertainty bars (taught).
• Constructing lines of maximum and minimum gradient by eye (taught).
• Determining the uncertainty in gradients and intercepts (taught).
• Linearizing graphs, only where appropriate (taught).
• Drawing lines of best fit (practised).
• Plotting graphs with appropriate scales and axes (practised).
• Propagating uncertainties in processed data (practised).
• Identifying and discussing sources and impacts of random and systematic errors (practised).

What’s in the pack

• Student Worksheet (31 pages) and Teacher Key (45 pages)
• The editable worksheet

Written against the IB DP Physics guide at Standard and Higher Level, so one pack serves a mixed class. It declares no topic and no understanding, deliberately: this belongs to the IB skills in the study of physics (Tool 3: Mathematics, with Inquiry 3), which is why Paper 1B and the internal assessment lean on it. Ages 16 to 19, as homework, reference or revision.

Related resources:

• Uncertainties, the pack that teaches the arithmetic this one assumes
• Measuring the Acceleration of Free Fall, the practical it serves (free)
• Graphical Analysis of Motion, where plotting is taught