I have a question regarding the effect of individual participant related differences. Whats the best way to discuss their effect?
For example a researcher used an all female sample, for the study of the memory ability of the population: students.
Do you say: 'The use of an all-female sample is considered an extraneous (and potential confounding) variable because the results of the participants are unrepresentative of the characteristics of the population (students), this therefore compromises the external validity of the experiment as the findings cannot be accurately generalised to the population of research interest. ' or do you say: 'Having an all-female sample can be considered an extraneous (and potential confounding) variable because this characteristic may influence the results, as the cause of change in the dependent variable (memory abilities of the participants), may be due to the fact that they are female, and not due to the effect of the independent variable, this therefore reduces the internal validity of the experiment, as this characteristic could potentially have had an effect on the dependent variable.'