AH Biology - Unit 3 - KA2(d) - Reliability

Why is there normally variation in repeats of results?

There is normally variation in repeats of results due to:

• Natural variation in the population

• Reliability in the measurement methods

How can the reliability of measuring instruments and procedures be determined?

The reliability of measuring instruments and procedures can be determined by taking repeated measurements or readings of an individual data point.

From repeated measurements or readings of an individual data point what can be determined?

From repeated measurements or readings of an individual data point, the precision of the equipment or procedure can be determined.

What does it mean if all the readings of an individual data point are really close together?

If all the readings of an individual data point are really close together then the equipment or procedure is precise. However, it does not mean it is accurate. For example, if a pH meter is not calibrated, it might consistently read the same incorrect pH again and again.

How can natural variation in biological material be determined?

Natural variation in biological material can be determined by measuring a sample of individuals from a population.

What does the mean of repeated measurements from a sample of individuals from a population give an indication of?

The mean of repeated measurements from a sample of individuals from a population gives an indication of the true value being measured.

What is the range of values around the mean of repeated measurements from a sample of individuals from a population a measure of?

The range of values around the mean of repeated measurements from a sample of individuals from a population is a measure of the extent of the variation. A narrow range would indicate low variation within a population.

What is an independent replicate?

An independent replicate is when the full experiment is repeated using a different group of individuals, freshly made solutions, etc. on a different day.

What should independent replicates be carried out to produce?

Independent replicates should be carried out to produce an independent data set.

What can independent data sets be used to determine?

Independent data sets can then be compared to determine the reliability of the results.

What is the relationship between the similarity of independent data sets and reliability of results?

The relationship between the similarity of independent data sets and reliability of results is that the more similar the independent data sets are, the more reliable the results are.

What is needed for overall results to be considered reliable?

Overall results can only be considered reliable if they can be achieved consistently.