Hypothesis and experimentation

A hypothesis is a possible explanation that can be tested by experiment. In exams identify testability.

The amount of light is changed by the student so it is the independent variable. In exams find the factor deliberately changed.

Plant growth is measured as a result of changing light so it is the dependent variable. In exams identify the measured outcome.

Keeping controlled variables constant makes the effect of the independent variable clear. In exams focus on fair comparison.

The first statement gives a testable relationship between two variables. In exams identify testable if-then statements.

Keeping the seed type the same allows a fair test of water amount. In exams keep other conditions constant.

Repetition reduces the influence of unusual results and gives a more dependable average. In exams link reliability with repetition.

Revising or rejecting an unsupported hypothesis and testing again is part of science. In exams follow evidence rather than expected results.

The amount of stain removed is the measured outcome so it is the dependent variable. In exams choose the variable measured as the effect.

A written procedure allows the experiment to be repeated using the same steps. In exams link reproducibility with procedure.

Quantitative data is information expressed through numbers and, when appropriate, a unit. It tells how much, how long, how tall, how heavy or how many, so it can be measured and compared more precisely. Descriptions such as colour, smell or surface feel are generally qualitative observations because they use words rather than a numerical measurement.

Option D is correct: a plant height of twelve centimetres contains the numerical value 12 and the unit centimetres. The statements that the solution is blue, the smell is strong and the leaf is smooth describe qualities, not measured amounts. A colour or texture could sometimes be studied using instruments, but as written these choices are qualitative descriptions. Thus, the number-and-unit observation is the quantitative datum.

Changing one variable at a time allows the result to be linked to that variable. In exams look for cause and effect.

This statement gives a testable relationship between temperature and evaporation. In exams check that both variables are clear.

An average combines several readings to give a typical value and reduce random variation. In exams link averages with reliability.

Safety goggles protect the eyes from chemical splashes. In exams match safety equipment with the risk.

A testable hypothesis contains variables that can be controlled and measured. In exams look for observable evidence.

The type of surface is deliberately changed so it is the independent variable. In exams choose the factor changed by the experimenter.

A value very different from the other readings is called anomalous. In exams check it and repeat the measurement if needed.

The conclusion states from the data whether the hypothesis was supported. In exams give an evidence-based answer.

A stopwatch measures time so it records the dissolving time. In exams correctly match apparatus with the quantity measured.

A calibrated and suitable instrument gives measurements closer to the true value. In exams link accuracy with proper apparatus.

A suitable graph shows the relationship between two quantitative variables. In exams place the independent and dependent variables on the axes.

Correcting for zero error makes measurements more accurate. In exams check the zero reading before use.

An observation is direct evidence whereas an inference interprets that evidence. In exams separate fact from explanation.

Keeping the initial amount of water the same allows a fair comparison of location. In exams keep all conditions except the tested factor constant.