Understanding Clinical Trial Design - Research Advocacy Network

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UNDERSTANDING CLINICAL TRIAL DESIGN: A TUTORIAL FOR RESEARCH ADVOCATES
Pivotal Trial A controlled trial to evaluate the safety and efficacy of a
drug in patients who have the disease or condition to be
treated.
Placebo An inactive substance or treatment that looks the same
as, and is given the same way as, an active drug or
treatment being tested. The effects of the active drug or
treatment are compared to the effects of the placebo.
Population The entire collection of people (current and future) who
are the focus of interest (e.g., all people with a specific
type of cancer).
Population A value of some quantitative characteristic in a
Parameter population. Population parameters are estimated by
sample statistics calculated from sample data (e.g.,
sample mean).
Posterior Probability The posterior probability is the conditional probability
of a variable, taking the evidence into account. The
posterior probability is computed from the prior
probability and the likelihood function via Bayes’
theorem.
Power Power is the probability of rejecting the null hypothesis
if it is really false. It is mathematically equal to 1 - b and
is dependent upon the sample size, sample variance, the
effect size and type II error rate.
Prevalence The total number of existing cases of a disorder as a pro
portion of a population (usually per 100,000 people) at
a specific time.
Primary Endpoint The main result that is measured to see if a given
treatment worked (e.g., the number of deaths or the
difference in survival between the treatment group and
the control group). The primary endpoint is determined
by the primary study objective, and is defined prior to
the start of the trial.
Prior Probability A prior probability is a base rate, interpreted as a
description of what is known about a variable in the
absence of some evidence.
Probability The likelihood that a given event will occur. Probability
is expressed as values between 0 (complete certainty that
an event will not occur) to 1 (complete certainty that an
event will occur), or percentage values between 0 and
100%.