A good IA idea is not a clever title. It has one clear variable, measurable data, a model or method from the subject, enough repeats and a limitation you can evaluate honestly.
Before choosing a topic, ask whether you can control one independent variable, measure one dependent variable, test a model, collect enough data and explain a real limitation. Add a personal angle only when it helps the investigation instead of forcing it.
If the idea cannot produce a table, graph, calculation and evaluation paragraph, it is not ready for teacher approval.
Math IAs work when the mathematics does real work: modelling, optimisation, regression, derivation, proof or comparison. Physics IAs work when the setup is controlled enough that uncertainty does not bury the effect.
Weak IA ideas are usually too broad, impossible to control, unsafe, dependent on equipment you cannot access, or dressed up with advanced maths that does not explain the data.
For retake students, remember that IBretake does not arrange IA supervision. If changing IA matters to your grade, confirm the option with your school or coordinator before assuming a host school can do it.
Before writing the introduction, make a one-page plan: research question, variables, equipment, method, data table, model, graph, uncertainty and evaluation limitation.
If that page looks vague, change the topic while it is still cheap to change.
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