Question

1) A. What are research methods and the important elements of research design (i.e. describe population vs sample, indicators/measures, counter factual, time of measurement and analysis).

B. What are internal validity, external validity and reliability and how do they relate to the concept of research methods?

C. Compare and contrast three of the following types of research designs: Single subject, true experimental group design, quasi experimental group design, non-experimental design.

Answer each part of the question.

Answer 1

1)

A.  

Population vs Sample

The main difference between a population and sample has to do with how observations are assigned to the data set.

• A population includes all of the elements from a set of data.
• A sample consists one or more observations drawn from the population.

Depending on the sampling method, a sample can have fewer observations than the population, the same number of observations, or more observations. More than one sample can be derived from the same population.

Indicators measures

The indicator function of an event is a random variable that takes value 1 when the event happens and value 0 when the event does not happen. Indicator functions are often used in probability theory to simplify notation and to prove theorems.

Counterfactual Analysis

In the counterfactual analysis, the outcomes of the intervention are compared with the outcomes that would have been achieved if the intervention had not been implemented. The method of counterfactual impact evaluation allows to identify which part of the observed actual improvement (e.g. increase in income) is attributable to the impact of the intervention (since such improvement might occur not only due to the intervention but also due to other factors, e.g. overall economic growth).

B.

Internal Validity

Validity is described as the degree to which a research study measures what it intends to measure. There are two main types of validity, internal and external. Internal validity refers to the validity of the measurement and test itself, whereas external validity refers to the ability to generalise the findings to the target population. Both are very important in analysing the appropriateness, meaningfulness and usefulness of a research study.

If the results of a study are not deemed to be valid then they are meaningless to our study. If it does not measure what we want it to measure then the results cannot be used to answer the research question, which is the main aim of the study. These results cannot then be used to generalise any findings and become a waste of time and effort. It is important to remember that just because a study is valid in one instance it does not mean that it is valid for measuring something else.

C

An experiment is so because it contains both experimental group and control group.

True experimental design is a design that involves the manipulation of the independent variable and comparison of groups in randomized assignment.

Quasi-experimental designs are designs that involve manipulation of the independent variable and may include comparison of groups but are absent in randomized assignment of subjects to conditions.

The similarity between a true experiment and a quasi-experiment is that both of them contain an experimental group and a control group.

The difference in that a true experiment has probability samples and a quasi-experiment involves a non-probability sample.

The word experiment is a broader term because it could include a pre-experiment, (which is not actually an experiment), a quasi-experiment and a true experiment.