Core Competencies: Choosing Study Design Dr. Jackson K. Mukonzo, MSc. Pharm, Ph.D

Before starting…….. Is there a problem? – Do you have a research question? What do you want to do about the problem? How do you want to do it?

Research Design Internal validity as opposed to external validity: Research Design refers to the plan, structure, and strategy of research--the blueprint that will guide the research process. Internal validity as opposed to external validity: Researcher ability to draw, correct/accurate conclusions from the research.

Study design: How? A study design is a specific plan or protocol for conducting the study, which allows the investigator to translate the conceptual hypothesis into an operational one.

Choice of Design Research Question(s) Research Goal(s) Researcher Beliefs and Values Researcher Skills Time and Funds Ethical Limitations Status of Existent Knowledge Occurrence of Disease Duration of Latent Period Nature and Availability of Information Available Resources

Types of Study Designs Qualitative Quantitative Experimental Observational Basic Hybrid Incomplete

Quantitative No! Qualitative Are you interested in meaning of experiences or just describing? Understanding -words and anlysis Real world experience Open-ended and flexible rich data Quality of informant more important than sample size Subjective Quantitative Prediction- discrete Theory testing (experimental) Sample size core issue in reliability of data What you plan for is what get Objective Is any of the methods better than the other? No!

Qualitative Techniques Participant observation Gains insight into understanding cultural patterns to determine what’s necessary and needed in tool development (complementary to interviews) Interviews/Focus groups with stakeholders Explores how tools are used and could be used in a novice programming course Gains insight into the meaning of tools for students for learning to program

Quantitative Designs Analytical Descriptive Experimental Observational Cohort Cross-sectional Case-control Other Randomized Clinical Trial Non-randomized Descriptive Community Survey A fundamental issue is whether to observe the events taking place in the study subjects in an observational study or to apply an intervention and examine its effects of these events in a clinical trial. Among observational studies, two of the most common designs are cohort studies, in which a group of subjects is follower over time, and cross-sectional studies, in which the observations are made on a single occasion. A third common option is the case-control design, in which the investigator compares a group of subjects who have a disease or condition with another group of subjects who do not. Types of design: Some of the most popular designs are sorted below, with the ones at the top being the most powerful at reducing observer-expectancy effect but also most expensive, and in some cases introducing ethical concerns. The ones at the bottom are the most affordable and are frequently used earlier in the research cycle, to develop strong hypotheses worth testing with more expensive research approaches. Experimental Randomized clinical trial Double-blind Single-blind Non-blind Non-randomized clinical trial Non-experimental Cohort study Prospective cohort Retrospective cohort Nested cohort Case-cohort study Case-control study (case series) Nested case-control study Cross-sectional study Descriptive Community survey Descriptive studies- used to study variation in frequency by demographic characteristics, place & time Analytic studies researcher has a pre-specified hypothesis Experimental Studies are conducted under controlled conditions where researcher manipulates some measure Observational studies do not involve intervention Observe natural course of events where changes in one characteristic is studied in association with changes in other characteristics Often necessary when unethical or infeasible to manipulate exposure Will give more details about types of study design with examples later in talk after we discuss some issues to consider when selecting a study design

Analytic Studies We can use analytical studies to test hypotheses. We want to know: Whether there is an association between hypothesized exposure and disease, How strong the association is, What proportion of cases are due to exposure, and Whether there is an increased risk of disease with increased exposure (a dose-response relationship). Experimental or observational A previous FOCUS issue explained how to use information to generate a hypothesis (or educated guess) about the cause of an outbreak. But just as suspicion is not enough to warrant a conviction in a courtroom, you need evidence to support your hypothesis. In science, we use analytic studies to test hypotheses. This issue of FOCUS describes different types of study designs that can be used to test a hypothesis. Which one to choose is up to you…. In field epidemiology, we call the specific cause of an outbreak the “exposure.” We want to know whether there is an association between our hypothesized exposure and disease, how strong the association is, what proportion of cases are due to the exposure, and whether there is an increased risk of disease with increased exposure (also known as a dose-response relationship). These questions and others can be answered with the results of a well designed analytic study. Two commonly used types of analytic studies are the cohort study and the case-control study.

Quantitative designs Observational: studies that do not involve any intervention. Experimental: studies that entail manipulation of the study factor (exposure) and randomization of subjects to treatment (exposure) groups

Quantitative Designs Analytic Descriptive Experimental Observational Cohort Cross-sectional Case-control Other Randomized Clinical Trial Non-randomized Descriptive Community Survey A fundamental issue is whether to observe the events taking place in the study subjects in an observational study or to apply an intervention and examine its effects of these events in a clinical trial. Among observational studies, two of the most common designs are cohort studies, in which a group of subjects is follower over time, and cross-sectional studies, in which the observations are made on a single occasion. A third common option is the case-control design, in which the investigator compares a group of subjects who have a disease or condition with another group of subjects who do not. Types of design: Some of the most popular designs are sorted below, with the ones at the top being the most powerful at reducing observer-expectancy effect but also most expensive, and in some cases introducing ethical concerns. The ones at the bottom are the most affordable and are frequently used earlier in the research cycle, to develop strong hypotheses worth testing with more expensive research approaches. Experimental Randomized clinical trial Double-blind Single-blind Non-blind Non-randomized clinical trial Non-experimental Cohort study Prospective cohort Retrospective cohort Nested cohort Case-cohort study Case-control study (case series) Nested case-control study Cross-sectional study Descriptive Community survey Descriptive studies- used to study variation in frequency by demographic characteristics, place & time Analytic studies researcher has a pre-specified hypothesis Experimental Studies are conducted under controlled conditions where researcher manipulates some measure Observational studies do not involve intervention Observe natural course of events where changes in one characteristic is studied in association with changes in other characteristics Often necessary when unethical or infeasible to manipulate exposure Will give more details about types of study design with examples later in talk after we discuss some issues to consider when selecting a study design

Experimental Design time outcome Intervention no outcome Study RANDOMIZATION Intervention no outcome Study population outcome Control no outcome Experimental Design baseline future time Study begins here (baseline point)

Think more, Think Well, It Can be Easier! One of the simplest experimental designs is the ONE GROUP PRETEST-POSTTEST DESIGN--EXAMPLE? One way to examine Efficacy of a Drug: O1 X O2 Measure DRUG Measure Patients’ Condition Experimental Patients’ Condition (Pretest) Condition/ (Posttest) intervention RESULT: Significant Improvement from O1 to O2 (i.e., sig. O2 - O1 difference) QUESTION: Did X (the drug) cause the improvement?

Research question 1: Does perinatal exposure to TDF have any effect on bone development during the first 10 years of life? Study design? Research question 2: Does the use of a particular vaginal microbicide ring during pregnancy have any effect(s) on birth outcomes? Research question 3 Why is the up-take of contraceptive formulation X low in women ≤ 30 years of age

Questions or Comments ? As we saw from the Aids-Floridation example, the above two are not enough. We try to do it primarily through (statistical control and sample selection) to a lesser degree.