MYP Physics Criterion C: Collecting & Processing Data — FAQ

Most students collect data fine but lose marks on processing: no uncertainty shown, graphs missing units or best-fit lines, and conclusions that don't reference the actual numbers. Criterion C rewards precision and interpretation, not just a neat table — that's the part rushed under time pressure.

Collecting data means recording raw measurements accurately, with correct units and sensible precision (matching the instrument's smallest division). Processing means turning that raw data into something meaningful — averages, calculations, graphs, trend lines and uncertainty — that you then interpret against your original hypothesis.

The three repeat offenders: no uncertainty or error bars anywhere, a graph without a title/axis units, and a conclusion that says "the results support the hypothesis" without citing a single number from the data. Examiners can't award interpretation marks for claims that aren't backed by the actual figures.

A 7-8 needs data presented clearly with correct units, processing that includes uncertainty and appropriate maths (averages, percentage error, gradients), and a conclusion that critically interprets the results — explaining anomalies, not just describing the trend. Vague description without numbers caps you at a 5-6.

For a single reading, uncertainty is usually half the smallest division on your instrument (a ruler marked in mm gives ±0.5 mm). For repeated trials, use half the range: (highest − lowest) ÷ 2. Always state units and carry the uncertainty through to your final calculated value.

Use a descriptive title ("Graph to show..."), label both axes with quantity and unit, choose a scale that fills most of the page, and draw a single best-fit line or curve — not a dot-to-dot join. If plotting by hand, use a sharp pencil and a ruler for any linear trend.

Refer back to your original research question, state what the data actually shows (using a real number — a gradient, a percentage, an average), compare it to any accepted value or theory, and explain any anomalies with a scientific reason rather than "human error."

Criterion C — Processing and Evaluating — assesses three strands: presenting collected and transformed data (tables, graphs), processing data accurately (calculations, uncertainty), and interpreting results with scientific reasoning to judge validity. It's marked out of 8, using the MYP Sciences criterion descriptors for the appropriate year.

The strands stay the same, but the sophistication expected rises. MYP 4-5 students are expected to handle multiple variables, quantify uncertainty numerically rather than just noting sources, and evaluate the validity of the method itself — not just describe what happened.

Criterion B assesses your planning — the hypothesis, variables, and method design — before you collect anything. Criterion C only kicks in once you have data: it's about how accurately you present, calculate with, and interpret what you actually measured, regardless of how good the original plan was.

Criterion C is a skills gap, not a content gap — your child likely understands the physics but hasn't practised the specific habits (stating uncertainty, labelling graphs, quoting numbers in conclusions) that examiners are trained to look for. It's fixable with targeted practice, not more content revision.

The fastest improvement comes from redoing old lab write-ups against the actual criterion descriptors rather than starting new experiments. Have your child mark their own past work against the strand i–iii language, then rewrite just the graph or conclusion section. Topical worksheets on RevisionPrep give short, markable Criterion C-style tasks for exactly this kind of repetition.