IA idea · Statistics & hypothesis testing

Are NBA players getting taller?

AI SLAI HLAA SLAA HL Accessible Also in: Sport

Research question

Has the mean height of NBA players changed significantly between the 1980s and the 2020s, and are heights still normally distributed?

Adapt it: change the place, the data or the comparison until the question is yours.

Why it makes a good exploration

Basketball has changed from towering centres to fast shooters. Height data for every player lets you test whether the players themselves have changed — and whether the normal distribution still fits.

The mathematics you'll need

Normal distribution and z-scores
Histograms and normal probability comparisons
Two-sample t-test
Chi-squared goodness-of-fit to a normal distribution

Course labels show where a technique sits; using maths from outside your course is fine if you explain it clearly and say it is new to you.

Where the data comes from

Collect player heights for chosen seasons from Basketball Reference.

Basketball Reference — NBA player and team statistics back to 1946, exportable tables.

Cite every source in a footnote where you use it and in your bibliography. Check the licence of any dataset you download.

A possible outline

Define the populations (players who played in a season).
Describe both distributions.
Test the difference in means.
Test normality of each.
Reflect on changes in how heights are measured and reported.

Pitfalls that cost marks

Counting players multiple times across seasons.
Using listed heights without noting that measurement rules changed.
Assuming normality.

Showing personal engagement

Compare players in your favourite team or position.
Predict how many players are over 7 ft using your normal model and check.
Compare with average adult heights.

See Criterion C: personal engagement for what examiners look for.

Taking it further

Compare distributions by position and discuss whether a mixture of normals fits better.

Turn this idea into your IA

Plan this IAOpens the planner with this question, the maths and data sources filled in. Desmos workspacePlot your data, fit models and keep your graphs with your plan. AI feedback on a draftCriterion-by-criterion feedback with evidence from your own text. Coaching, not rewriting. Examiner reviewPete, a practising IA examiner, reads your draft and talks it through with you (€100).