# Experimental study design Randomised Controlled Trials MSc Physician Associate Practice Master’s Phy Flashcards

Descriptive epidemiology tends to focus on?

generating hypotheses

Analytical epidemiology tends to focus on?

Testing hypotheses

What is descriptive epidemiology?

Descriptive Epidemiology is the study of the amount and distribution of

disease or other health-related characteristics in human populations by

person, place and time.

Descriptive epidemiology identifies who is affected,

when, and where the situation is occurring in the community or population

of interest. This is an important tool for health services planning and

programming.

What is an experimental study?

A study in which conditions are under the direct control of the investigator.

In epidemiology a study in which a population is selected for a planned trial

of a regimen whose effects are measured by comparing the outcome of the

regimen (e.g. new medication) in the experimental group with the outcome

of an alternative regimen (standard) in a control group.

To avoid bias in experimental studies what should take place?

To avoid bias, members of the experimental and control group should be

comparable in all variables except in the regimen that is offered them.

Allocation of individuals to experimental and control groups is ideally by

randomisation.

Most common experimental studies

- Randomised controlled trial (individuals)
- Community trials (communities, clusters)

Since the interventions are strictly determined by the study protocol, ethical

considerations are of paramount importance in the design of these studies. True or false?

True

What experimental study is the most reliable study design? Why?

Randomised controlled trial.

Most reliable study design due to randomisation and control of all other

variables except for the intervention (eliminates confounding)

• Regarded as the golden standard among primary study designs

Golden standard primary study design?

RCT

In RCT, groups are followed up to see how effective the experimental intervention was. Outcomes are measured at specific times and any difference in response between the groups is assessed statistically.

This method is also used to reduce ?

Bias

What does H0 tell?

Null hypothesis – almost always no difference between the two treatments

What does H1 tell?

Alternative hypothesis

What do all hypotheses tests use to weigh the strength of the

evidence (what the data is telling you about the population)?

P- value

What is the p value.

The p-value is a number between 0 and 1 and interpreted in the following

way:

– A small p-value (typically < 0.05) indicates strong evidence against the null

hypothesis, so you reject the null hypothesis. Thus you accept the alternative

hypothesis

– A large p-value (typically > 0.05) indicates weak evidence against the null

hypothesis, so you fail to reject the null hypothesis. Thus you accept the null

hypothesis

P values indicate the believability that the null hypothesis is true given the sample

data. True or false?

True

Why are P-values are an integral part of inferential statistics ?

P-values are an integral part of inferential statistics because they help you use your

sample to draw conclusions about a population.

Statistically significant means the difference is large or

scientifically / clinically important, true or false?

False

What type of question is statistical significance?

Mathematical

What type of question is a Clinical importance?

- Requires clinical judgment

– Must be considered & addressed before it is possible to ask about

statistical significance

Randomisation should equally distribute any

confounding variables between the two groups, although it is important to be

aware that differences in confounding variables may arise through?

chance