GED and HiSET Science — experiments, results and content

Both exams list experimental reasoning alongside content knowledge, and it is the half that revision usually skips. You can know what mitochondria do and still lose a question that asks which of four described experiments would actually test a hypothesis. Four of these ten are about that, and six are content.

The experimental four start easy and get harder. A gardener with ten seedlings, five given fertiliser and five given water — what is the variable she chose to change? A delivery driver who suspects hills cost him fuel — which of four proposed tests would isolate the hill from everything else? A cafe's customers and coffees over five days — what do ten numbers license you to say, and why is profit not one of them?

The fourth is the one worth sitting with. A haulage firm puts a new engine oil in its ten newest lorries and leaves the old oil in its ten oldest, then finds the newer ones used six per cent less fuel. Two things differ between those groups, not one, and no amount of care in the measurement separates them. The answer that reads the six per cent as the oil's effect is the mistake; so, in the other direction, is concluding that age makes no difference. The repair takes one sentence, and the explanation gives it.

The content six cover what recurs on both papers: which part of a cell releases energy from nutrients and which parts spend it, what decomposers do in an ecosystem, what makes burning a chemical change while melting and dissolving are not, which force opposes a box being pushed across a floor, evaporation in the water cycle, and how igneous rock forms.

The contexts are adult ones — a garden, a delivery round, a cafe, a haulage yard — and every experiment and every figure is described in words, since there are no diagrams here. The real papers use graphs and tables heavily, and for that specific skill the free practice tests both organisations publish are the right place to go.

Zestly is an independent study tool. It is not affiliated with GED Testing Service or with PSI Services, and it is not a test centre.

• Identify the independent variable in a described experiment, and tell it from what was measured and what was held constant
• Choose, from several described designs, the one that actually isolates the factor a hypothesis is about
• Spot a confounded comparison where two things differ at once, and say how to redesign it
• Say what a set of results does and does not establish, rejecting both the causal over-reading and the generalisation past its conditions
• Read a small data set for the relationship it shows, and see why sales are not profit
• State what releases energy in a cell, what decomposers return to an ecosystem, and what distinguishes a chemical change from a physical one
• Name the force that opposes sliding motion, the stage of the water cycle driven by heat, and how igneous rock forms

A haulage firm wants to know whether a new brand of engine oil reduces fuel use. It puts the new oil in its ten newest lorries and leaves the old oil in its ten oldest. Over the following month the ten newer lorries use 6 per cent less fuel per mile than the ten older ones. What does this result establish?