STUDY TYPES(DESIGNS)

By Blanca Estela Marroquín Valiente

UNIVERSITY OF EL SALVADORWESTERN MULTIDISCIPLINARY CAMPUSLANGUAGE DEPARTMENT

RESEARCH METHODS

CLASS 6 OF UNIT II

The type of study chosen depends on: the type of problem; the knowledge already available about the problem; and

the resources available for the study.

II. OVERVIEW OF STUDY TYPES

1. Exploratory studies 2. Descriptive studies 3. Comparative (analytical) studies4. Correlational research 5. Causal-comparative research6. Experimental Research7. Explanatory Research

1. Exploratory studies

1. An EXPLORATORY STUDY is a study of relatively short duration, which is carried out when little is known about a situation or a problem. It may include description as well as comparison.

For example: A national Acquired Immunodeficiency Syndrome (AIDS) Control Programme wishes to establish counseling services for Human Immunodeficiency Virus (HIV) positive and AIDS patients, but lacks information on specific needs patients have for support. To explore these needs, a number of in-depth interviews are held with various categories of patients (males, females, married, single) and with some counselors working on a programme that is already under way.

Exploratory studies gain in explanatory value if we approach the problem from different angles at the same time. This is called triangulation; it may be very useful to include observations and interviews. In this manner, information from different independent sources can be cross-checked.

2. Descriptive studies

2. A DESCRIPTIVE STUDY involves describing the characteristics of a particular situation, event or case.

a) descriptive case studies Descriptive case studies describe in-depth the characteristics of one or a limited number of ‘cases’. A case may be, for example, a patient, a health center, a school, or a village. Such a study can provide quite useful insight into a problem.

descriptive case studiesHowever, if one wishes to test whether the findings pertain to a larger population, a more extensive, cross-sectional survey has to be designed.

b) cross-sectional surveys Cross-sectional surveys aim at describing and quantifying the distribution of certain variables in a study population at one point of time. They may cover, for example:

cross-sectional surveys Physical characteristics of people, Socio-economic characteristics of people such as their age, education, marital status, number of children and income,

The behavior or practices of people and the knowledge, attitudes, beliefs, opinions which may help to explain that behavior, or

Events that occurred in the population.

cross-sectional surveys Cross-sectional surveys cover a selected sample of the population. If a cross-sectional study covers the total population it is called a census.

cross-sectional surveys Cross-sectional surveys cover a selected sample of the population. If a cross-sectional study covers the total population it is called a census.

3. Comparative or analytical studies

3. An ANALYTICAL STUDY attempts to establish causes or risk factors for certain problems. This is done by comparing two or more groups, some of which have developed the problem and some of which have not.

Types of analytical studies

a) Cross-sectional comparative studies Many cross-sectional studies focus on describing as well as comparing groups.

For example, a survey on malnutrition may wish to establish:

Cross-sectional comparative studies The percentage of malnourished children in a certain population;

Socio-economic, physical, political variables that influence the availability of food;

Feeding practices; and The knowledge, beliefs, opinions that influence these practices.

Cross-sectional comparative studies The researcher will not only describe these variables but, by comparing malnourished and well-nourished children, he will try to determine which socio-economic, behavioral and other independent variables may have contributed to malnutrition.

b) Case-control studies In a CASE-CONTROL STUDY the investigator compares one group where the problem that he wishes to investigate is present,

(e.g. malnutrition) and another group called a control or comparison group, where the problem is absent, in order to find out what factors have contributed to the problem.

(children who died within the first month of life) and ‘controls’ (children who survived their first month of life)

c) Cohort studies In a COHORT STUDY, a group of individuals that is exposed to a risk factor (study group) is compared to a group of individuals not exposed to the risk factor (control group).

The researcher follows both groups over time and compares the occurrence of the problem that he expects to be related to the risk factor in the two groups to determine whether a greater proportion of those with the risk factor are indeed affected.

The control group should be selected at the same time as the study group, and both should be followed with the same intensity.

A well-known example of a cohort study is the study by Doll and Hill (1950) of smokers and non-smokers that was conducted among doctors to determine the importance of smoking as a risk factor for developing lung-cancer.

4. Correlational research It attempts to determine whether and to what degree, a relationship exists between two or more quantifiable (numerical) variables. However, it is important to remember that just because there is a significant relationship between two variables it does not mean that one variable causes the other.

examples

The relationship between intelligence and self-esteem.

The relationship between anxiety and achievement.

The use of an aptitude test to predict success in an algebra course.

5 Causal-comparative research

attempts to establish cause-effect relationships among the variables of the study. The attempt is to establish that values of the independent variable have a significant effect on the dependent variable.

This type of research usually involves group comparisons. The groups in the study make up the values of the independent variable; for example, gender (male versus female), preschool attendance versus no preschool attendance, or children with a working mother versus children without a working mother. These could be the independent variables for the sample studies listed below.

However, in causal-comparative research the independent variable is not under the experimenter’s control; that is, the experimenter can't randomly assign the subjects to a gender classification (male or female) but has to take the values of the independent variable as they come. The dependent variable in a study is the outcome variable.

examples The effect of preschool

attendance on social maturity at the end of the first grade.

The effect of having a working mother on school absenteeism.

The effect of gender on algebra achievement.

6. Experimental research like causal-comparative research attempts to establish cause-effect relationship among the groups of subjects that make up the independent variable of the study, but in the case of experimental research, the cause (the independent variable) is under the control of the experimenter.

That is, the experimenter can randomly assign subjects to the groups that make up the independent variable in the study. In the typical experimental research design the experimenter randomly assigns subjects to the groups or conditions that constitute the independent variable of the study and then measures the effect this group membership has on another variable, i.e. the dependent variable of the study.

examples The comparative effectiveness of

personalized instruction versus traditional instruction on computational skill.

The effect of positive reinforcement on attitude toward school.

In an EXPERIMENTAL STUDY, individuals are randomly allocated to at least two groups. One group is subject to an intervention, or experiment, while the other group (s) is not. The outcome of the intervention (effect of the intervention on the dependent variable/problem) is obtained by comparing the two groups

example a researcher plans to study the effect of a new drug. (The drug has already been tested extensively on animals and has been approved for trial use.) He plans to include 300 patients in the study who are currently receiving the standard treatment for the same condition for which the new drug has been designed.

He explains the study to the patients asking their consent to be divided into two groups on a random basis. One group will receive the experimental drug while the other group will continue to receive the standard treatment. He makes sure that the medications are disguised and labeled in such a manner that neither the research assistant administering them nor the patient know which drug is used. (This is called a ‘double blind’ experiment.)

In real life settings, it is often impossible to assign persons at random to two groups, or to maintain a control group. Therefore, experimental research designs may have to be replaced by quasi-experimental designs.

Another type of design that is often chosen because it is quite easy to set up uses only one group in which an intervention is carried out. The situation is analyzed before and after the intervention to test if there is any difference in the observed problem.

7. Explanatory Research It attempts to establish the causes of the events, incidents or phenomena under study.

For example: electoral preferences (number of persons who will vote for certain candidate, age and gender of voting people)