Research Design

Research design is the overall plan or the blue print, created by researchers to answer the question.

it is the plan that guides the researcher in conducting his study

It includes the following: Research setting Sample and method of selection Types of data to be collected & instruments used for data

collection Strategies to control extraneous variables Description of tool and statistical treatment of data

Most of the research questions can be classified into 3 categories:

1.Questions that seek to describe a phenomenon or population2. Questions that seek to quantify the nature of relationship

between variables and subject3. Questions that seek to investigate the causality or the effects

of interventions.

Quantitative Research DesignCausality Causes of health related phenomena usually are not

deterministic but rather probabilisticExample:There is an ample evidence that smoking is cause of lung cancer,

but not everyone who smokes develops lung cancer and not everyone with lung cancer was a smoker.

Counterfactual what would happen to the same people exposed to causal factor

if they simultaneously were not exposed to causal factor

Criteria for CausalityLazarsfeld’s Criteria of causality1. Temporal- A cause must precede an effect.2. There must be an empirical relationship between presumed

cause and presumed effect3. The relationship cannot be explained as being caused by a

third variable.

Bradford Hill Criteria of causality:1. Temporal2. Strength- The stronger the association, the more likely it is that the

relation of "A" to "B" is causal 3. Dose-Response Relationship -An increasing amount of exposure

increases the risk4. Consistency- having similar levels of statistical relationship in several

studies.5. Plausibilty-evidence from laboratory or basic physiologic studies that a

causal pathway is credible6. Consideration of alternate explanation- consider multiple hypotheses

before making conclusions about the causal relationship 7. Experiment8. Specificity-established when a single putative cause produces a specific

effect.

9. Coherence- having similar evidence from multiple resources

Research Design Terminology in social scientific & medical literature

3 Major types of Quantitative Research Design

1. Experimental Design2. Quasi-experimental Design3. Non-experimental Design

Experimental Design Researchers are active agents, not passive observer 2 groups are formed: 1.) a control group and 2.)

experimental group. Two groups are formed through random assignment .

True experiment or RCT design has 3 properties:1. Manipulation- investigator manipulates or does something to

the independent variable2. Control-researcher exerts control over the setting and

situation. The control group does not receive any experimental treatment.

3. Randomization- giving every subject an equal chance of being selected as member of either group.

Control

• Control is achieve in an experimental study by manipulating, randomizing, by carefully preparing the experimental protocols and by using the control group.

Control group- group of participants whose performance on an outcome is used to evaluate that of the treatment group on the same outcome.

Experimental group- the group that receives intervention.

Possible counterfactual approach:

1. Alternative intervention- (ex. The participants would receive 2 different types of distractions as alternative therapies for pain.

2. Placebo- presumed to have no therapeutic effect. (ex. Hatfield (2008) study the effect of sucrose on infant pain responses during immunizations. He randomly assigned infants to groups administered either sucrose solution or sterile water.)

3. Standards method of care- patient receive usual procedures used to care for patients.

4. Dose-response effect- all participants get some intervention, but the experimental group gets intervention that is richer, more intense or longer

5. Wait-list control group- the control group would receive the full intervention after all research outcomes are assessed.

Randomization

Examples:Toss coin Draw lots Table of random numbers

Permuted Block randomization- randomization occurs blocks for participants.

Example: A block of size 12 would contain 6 A and 6 B with a

ratio of 1:1 or 8 A and 4 B with a ratio of 2:1

• Randomized consent or Zelen Design- “randomizing the patient first then obtain consent”. Intervention group are asked for consent for intervention and if control group are receiving standard care, consent is not necessary anymore.

• Blinding or masking- concealing information from participants, data collectors, care providers, intervention agents or data analysts to enhance objectivity and minimize bias.