Key concepts

Ex post facto designs are often used when the researchers do not have control over the selection and manipulation of the independent variable. this is why researchers look at the type and/ or degree of relationship between the 2 variables rather than at a cause-and-effect relationship.

Expert sampling is a type of purposive sampling technique that is used when your research needs to glean knowledge from individuals that have particular expertise. This expertise may be required during the exploratory phase of qualitative research, highlighting potential new areas of interest or opening doors to other participants. Alternately, the particular expertise that is being investigated may form the basis of your research, requiring a focus only on individuals with such specific expertise. Expert sampling is particularly useful where there is a lack of empirical evidence in an area and high levels of uncertainty, as well as situations where it may take a long period of time before the findings from research can be uncovered. 

an extraneous variable refers to any variables that you are not intentionally studying (or cannot study, perhaps because of reasons of cost or difficulty). Rather than there being just a few of these extraneous variables, there are likely to be hundreds or even thousands. In other words, it is impossible to avoid extraneous variables.

Extraneous variables can be defined as any variables that may affect the outcome of a study that were not manipulated by the researcher. These variables may be referred to as third variables and the research design of a study should control for them

Extraneous Variables are undesirable variables that influence the relationship between the variables that an experimenter is examining. Another way to think of this, is that these are variables the influence the outcome of an experiment, though they are not the variables that are actually of interest. These variables are undesirable because they add error to an experiment. A major goal in research design is to decrease or control the influence of extraneous variables as much as possible.

Extraneous Variables (or Intervening variable) are undesirable variables that influence the relationship between the variables that an experimenter is examining. These variables are undesirable because they add error to an experiment. A major goal in research design is to decrease or control the influence of extraneous variables as much as possible.

E.g. What is the students' performance (DV) when CLT (communicative language teaching) (IV) is applied to teaching grammar?

=> motivation, tiredness, boredom, preference for the instructor's teaching style, the student's learning style are extraneous variables

Extraneous Variables are undesirable variables that influence the relationship between the variables that an experimenter is examining. Another way to think of this, is that these are variables the influence the outcome of an experiment, though they are not the variables that are actually of interest. These variables are undesirable because they add error to an experiment. A major goal in research design is to decrease or control the influence of extraneous variables as much as possible.

Extraneous Variables are undesirable variables that influence the relationship between the variables that an experimenter is examining. Another way to think of this, is that these are variables the influence the outcome of an experiment, though they are not the variables that are actually of interest. These variables are undesirable because they add error to the experiment. A major goal in research design is to decrease or control the influence of extraneous variables as much as possible.

Extraneous Variables are undesirable variables that influence the relationship between the variables that an experimenter is examining.

Extraneous Variables are undesirable variables that influence the relationship between the variables that an experimenter is examining. Another way to think of this, is that these are variables the influence the outcome of an experiment, though they are not the variables that are actually of interest. These variables are undesirable because they add error to an experiment. A major goal in research design is to decrease or control the influence of extraneous variables as much as possible.