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What does validity mean in a scientific investigation?
Validity refers to whether the investigation measures what it is intended to measure.
What does reliability mean in a scientific investigation?
Reliability refers to how consistent the results are when the investigation is repeated.
Can an investigation be reliable but not valid?
Yes, results can be consistent but still not measure what was intended.
Can an investigation be valid but not reliable?
Yes, it may measure the correct variable but produce inconsistent results.
What type of variable must be kept constant to improve validity?
Controlled variables.
Which feature of an investigation most improves reliability: repeating trials or changing variables?
Repeating trials.
Why does increasing the number of trials improve reliability?
It reduces the effect of random errors and allows results to be averaged.
What happens to validity if more than one independent variable is changed at the same time?
Validity is reduced because the cause of the effect cannot be determined.
What is a systematic error?
A consistent error caused by faulty equipment or flawed method that affects validity.
What is a random error?
An unpredictable variation that affects reliability.
How can calibration of equipment improve an investigation?
It improves validity by ensuring measurements are accurate.
Why is averaging results from multiple trials useful?
It increases reliability by minimising the influence of random errors.
If results from an experiment vary widely between trials, what does this indicate?
Low reliability.
Why is controlling variables essential for drawing valid conclusions?
It ensures changes in the dependent variable are due only to the independent variable.
How does sample size affect reliability?
Larger sample sizes generally improve reliability.
Why might a biased sampling method reduce validity?
Because the sample may not represent the population being studied.
