Annotated exemplar · AI SL · deliberately mid-band
Sleep and reaction time: a mid-band draft, annotated to show how to improve
Exemplar written by IB Math Revision for teaching — do not submit or copy (academic misconduct). The data and the student voice are illustrative. Schools check coursework with similarity software such as Turnitin.
A deliberately mid-band draft on the same question as the full statistics exemplar, with an annotation on every problem explaining how to fix it. Read the two side by side to see exactly what separates about 10/20 from about 18/20.
How this exemplar would be marked
| Criterion | Mark | Why |
|---|---|---|
| A · Presentation | 2/4 | Some coherence and some organisation: there is an introduction, body and conclusion, but no precise aim, padding in the introduction, raw data in the body and repeated calculations. |
| B · Mathematical communication | 2/4 | Some relevant notation, but calculator notation, undefined variables, missing units and an unlabelled graph. |
| C · Personal engagement | 2/3 | Some engagement — the student collected their own data — but no personal questions, predictions or decisions drive the work. |
| D · Reflection | 1/3 | Limited, generic reflection only at the end; contradictory results are not discussed. |
| E · Use of mathematics | 3/6 | Relevant techniques at the right level, but the line of best fit is not justified, the chi-squared test is invalid (expected frequencies below 5) and the conclusion from it is wrong. |
| Total | 10/20 | About 10/20. Every lost mark here is recoverable with the fixes in the annotations — see the full exemplar for what they look like in practice. |
Marks are our judgement of this teaching exemplar against the current criteria, explained criterion by criterion. They are not IB moderation results.
Excerpts with examiner annotations
Free sections are shown below with comments; the rest is in the full exemplar, available in the protected viewer with the IA package or a Pro plan.
Introduction
Sleep is defined as “a naturally recurring state of mind and body, characterized by altered consciousness, relatively inhibited sensory activity, reduced muscle activity and inhibition of nearly all voluntary muscles during rapid eye movement (REM) sleep”. There are four stages of sleep and a full cycle takes about 90 minutes. Reaction time is the time it takes to respond to a stimulus. It is important in sports and driving.
I chose this topic because I like sleep and I am interested in sport. The aim of my IA is to investigate sleep and reaction time.
In this IA I will use a scatter graph, a line of best fit, Pearson's correlation coefficient and a chi-squared test.
A How to improve: the aim is a topic, not a question. Rewrite it as something with an answer, e.g. “Is there a relationship between hours slept the night before and simple reaction time among students in my year?”
A How to improve: the definition of sleep is copied (and not cited) and does not help answer the aim — cut it. Padding costs conciseness.
C How to improve: “I like sleep” is not engagement. Say what actually made you curious, and make a prediction you can test.
E How to improve: do not list the techniques in advance; introduce each one when it becomes necessary and say why it is appropriate.
Data collection
I asked 22 people in my class and my friends how much sleep they got and then they did a reaction test on their phones. Here are the results:
| Person | Sleep | Reaction |
|---|---|---|
| 1 | 5.5 | 269 |
| 2 | 6.0 | 263 |
| 3 | 6.0 | 283 |
| 4 | 7.0 | 276 |
| 5 | 5.0 | 253 |
| 6 | 7.0 | 251 |
| 7 | 6.0 | 253 |
| 8 | 8.0 | 261 |
| 9 | 8.0 | 234 |
| 10 | 8.5 | 214 |
| 11 | 8.0 | 292 |
| 12 | 7.0 | 255 |
| 13 | 8.0 | 259 |
| 14 | 8.5 | 296 |
| 15 | 6.5 | 291 |
| 16 | 8.0 | 256 |
| 17 | 7.0 | 270 |
| 18 | 8.5 | 224 |
| 19 | 6.5 | 297 |
| 20 | 7.0 | 261 |
| 21 | 7.5 | 303 |
| 22 | 7.5 | 242 |
B How to improve: variables are never defined (sleep when? in what units? reaction time in ms? mean of how many attempts?). Define them before the data.
B How to improve: the graph has no axis labels, units or meaningful title, and uses the default style. Label everything and number the figure.
A How to improve: 22 rows of raw data in the body. Put a summary or sample here and the full table in an appendix.
E How to improve: different phones have different screen and touch delays, so the measurements are not comparable. Use one device (as the full exemplar does) and justify the sample size — 22 friends is small and not representative.
D How to improve: there is no description or interpretation of the graph. What does it show? Is it what you expected?
Line of best fit and correlation
In the full exemplar (about 1 page). Line of best fit from the GDC, then r. Open in the protected viewer
Chi-squared test
In the full exemplar (about 2 pages). A 3 × 3 chi-squared test with every expected value calculated by hand. Open in the protected viewer
Conclusion
In conclusion there is a negative correlation between sleep and reaction time but the chi-squared test showed that they are independent. My results were quite accurate. Limitations are that there may have been human error and I could have used more data. In the future I could also look at other factors like caffeine.
D How to improve: this is limited reflection — generic (“human error”, “more data”) and only at the end. Reflect after each result, explain the contradiction between the two findings, and say which limitation most affects your answer.
A How to improve: the conclusion does not answer a precise aim (because there wasn't one) and the two results contradict each other without comment.
C How to improve: caffeine is mentioned only as an afterthought. The full exemplar makes exactly this idea the heart of the exploration.
What would push it higher?
- Write a precise aim with an answer, and a prediction.
- Define every variable with units; measure reaction time on one device, as a mean of several attempts.
- Calculate and interpret r before fitting a line; interpret its strength.
- Check test conditions (expected frequencies ≥ 5); state conclusions as “evidence”, never “proof”.
- Reflect after every result, and make caffeine (or another variable you care about) part of the question.