3.3b Reporting and evaluating experimental design

Question 1

Method section

Answer 1

A method section should contain sufficient information to allow another investigator to repeat the work.

Question 2

Experimental design

Answer 2

The experimental design should address the intended aim and test the hypothesis.

Treatment effects should be compared to controls. An experimental design that does not address the intended aim or test the hypothesis is invalid.

Question 3

Confounding variables

Answer 3

Confounding variables should be taken into account or standardised across treatments.

Question 4

Validity and reliability

Answer 4

The validity and reliability of the experimental design should be evaluated. The validity of an experiment may be compromised when factors other than the independent variable influence the value of the dependent variable.

Question 5

What is Selection bias?

Answer 5

Selection bias is the selection of a sample in a non-random way, so that the sample is not representative of the whole population. Selection bias may have prevented a representative sample being selected.

Question 6

Sample size

Answer 6

Sample size may not be sufficient to decide without bias whether the change to the independent variable has caused an effect in the dependent variable.