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12 exam-style questions with model answers, plus 12 quick multi-choice questions — every question on the site for this standard, grouped by the 4 pages of notes they come from.
Write a full answer before you reveal the model one — that comparison is where the marks come from. Every block links back to the notes that teach it.
A researcher randomly gives half of 40 volunteers a caffeine drink and half a caffeine-free drink, then measures their reaction times. State the explanatory variable and the response variable.
Explain why the caffeine study is an experiment and not an observational study, and why that matters for the conclusion.
A newspaper reports that people who drink coffee have faster reaction times, based on surveying coffee drinkers and non-drinkers. Explain why this cannot show that coffee causes faster reactions, and how an experiment would fix it.
Name two features of a well-designed experiment and say briefly what each does.
In a plant experiment, the treatment plants were kept on a sunny windowsill and the control plants in a shaded corner. Explain what is wrong and how to fix it.
A student tests a new sports drink by giving it to the school's first XV and comparing their sprint times with the times of the chess club. Critique this design and redesign it fairly.
In an experiment, the treatment group's median yield is 15 kg and the control group's is 11 kg. State the observed difference.
The treatment group has median 15 kg (box 12–18) and the control 11 kg (box 9–14), on the same scale. Compare the groups and state what still needs checking.
Two students look at the same experiment. One says 'the treatment clearly works because its median is higher.' Explain why that reasoning is incomplete.
An experiment found that the treatment group's median reaction time was 0.04 seconds faster than the control group's.
Write the inference this supports.
In an experiment, the treatment median is only slightly higher than the control median, and the two box plots overlap almost completely.
What should you conclude, and why?
Twenty-four people were randomly allocated to two groups to test whether a stretching routine improves flexibility. The treatment group's median improved by 6 cm more than the control's, with limited overlap between the groups.
Write a full conclusion, and explain what you can and cannot claim.