Study

Validity and Reliability

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  • How does sample size affect reliability?
    Larger sample sizes generally improve reliability.
  • Why does increasing the number of trials improve reliability?
    It reduces the effect of random errors and allows results to be averaged.
  • What is a random error?
    An unpredictable variation that affects reliability.
  • What does validity mean in a scientific investigation?
    Validity refers to whether the investigation measures what it is intended to measure.
  • Why is validity particularly important when testing cause-and-effect relationships?
    Because invalid methods prevent accurate identification of causal links.
  • 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.
  • Does repeating an invalid experiment make it valid?
    No, repetition only improves reliability, not validity.
  • What does reliability mean in a scientific investigation?
    Reliability refers to how consistent the results are when the investigation is repeated.
  • What is one way to improve the validity of secondary data?
    Check the credibility of the source and compare with other reliable sources.
  • Why must conclusions be supported by data to be valid?
    Because conclusions not based on evidence are not scientifically justified.
  • If results from an experiment vary widely between trials, what does this indicate?
    Low reliability.
  • How can calibration of equipment improve an investigation?
    It improves validity by ensuring measurements are accurate.
  • Can an investigation be valid but not reliable?
    Yes, it may measure the correct variable but produce inconsistent results.
  • Which feature of an investigation most improves reliability: repeating trials or changing variables?
    Repeating trials.
  • What is a systematic error?
    A consistent error caused by faulty equipment or flawed method that affects validity.
  • Why is averaging results from multiple trials useful?
    It increases reliability by minimising the influence of random errors.
  • What type of variable must be kept constant to improve validity?
    Controlled variables.
  • Why is controlling variables essential for drawing valid conclusions?
    It ensures changes in the dependent variable are due only to the independent variable.
  • Can an investigation be reliable but not valid?
    Yes, results can be consistent but still not measure what was intended.
  • Why might a biased sampling method reduce validity?
    Because the sample may not represent the population being studied.
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