What the investigation does
Galaxy images and spectra are used to estimate the Hubble parameter and cosmic age, followed by a discussion of model assumptions and uncertainty.
What the examiner response highlights
Secondary astronomical data becomes student-owned analysis through image measurement, redshift calculation and small-angle reasoning.
Regression graphs, error bars and alternative trendlines make systematic uncertainty visible.
The conclusion recognizes the limits of constant expansion and treats the age estimate cautiously.
What to examine critically
Selecting galaxies partly because they produced values near the reference result introduces confirmation bias; assuming a common galaxy diameter is also crude.
A current version should define inclusion rules before fitting, use contemporary data and justify every uncertainty and unit choice.
How to use this example
Study the decisions behind the work: how the question is narrowed, what counts as evidence in this subject, how the line of argument develops, and where the evaluation becomes specific. Do not copy its wording, structure or method as a template.
Assessment changes for first examination in May 2027 redesign the criteria around the essay framework, knowledge and understanding, analysis and argument, discussion and evaluation, and reflection. Always check the requirements for your own session.
Essay & examiner commentary
Read online or save both PDFs to study alongside this breakdown.
Source & assessment context
These files come from the IB’s 50 More Excellent Extended Essays (2011). The essay and commentary retain their original attribution. Consult the current guide for your assessment session.
IB Extended Essay resources ↗Current Extended Essay updates ↗
