IA idea · Statistics & hypothesis testing

Are our summers getting wetter or drier?

AI SLAI HLAA SL Accessible Also in: Environment

Research question

Is mean summer rainfall at [a UK weather station] significantly different in 1991–2020 compared with 1961–1990?

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

Why it makes a good exploration

Climate normals are 30-year averages, and comparing two of them is exactly how meteorologists describe change. Met Office station records make this a clean, local two-sample test.

The mathematics you'll need

Descriptive statistics and box plots
Two-sample t-test and its assumptions (AI)
Linear regression of rainfall against year
Variability and standard deviation

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

Download monthly station data from the Met Office historic station pages and sum June–August each year.

Met Office historic station data — Monthly max/min temperature, rainfall, frost days and sunshine for 37 UK stations, some from 1853.

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

Explain the station and the data (including provisional values).
Compute summer totals and describe both periods.
Run the t-test; check assumptions.
Look at the trend and at variability, not just the mean.
Reflect on station changes and natural variability.

Pitfalls that cost marks

Missing months treated as zero.
Ignoring that rainfall is often skewed.
Over-claiming about climate change from one station.

Showing personal engagement

Choose the station nearest your home.
Compare with temperature at the same station.
Relate to a local flood or drought you remember.

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

Taking it further

Compare the variance of the two periods (are extremes more common?) or test several stations.

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).