••• CHAPTER 64^ Basic Epidemiology and Clinical Biostatistics^645
❍ What are group-randomized trials?
They are randomized trials where identifiable groups (eg, physician practices) rather than individuals are allocated
to treatment or control conditions.
❍ What are multicentered randomized trials?
They are RCTs conducted at multiple centers rather than a single center.
❍ Define clinical biostatistics.
Clinical biostatistics is the application of study design and statistical analysis in clinical medicine.
❍ What are the essential characteristics of a research question?
A research question must be feasible to study, interesting to both the researcher and the clinician, novel or
innovative, ethical, and relevant or worth doing.
❍ What are the essential characteristics of a hypothesis?
A hypothesis must be measurable, it should specify the population being studied, identify the time frame, indicate
the type of relationship being examined, include the variables (see below) being studied, and define the statistical
level of significance (defined later in chapter).
❍ What are variables?
Variables are characteristics of interest in a study that have recorded value(s) for each patient in the study. There are
two types of variables: quantitative and qualitative.
❍ What are quantitative variables?
Quantitative variables are also called continuous variables. They are measured on a scale in which a value could be
placed between any two numbers (can be measured to the decimal place).
❍ What are the two types of qualitative variables? Define each.
The two types of qualitative variables are nominal and ordinal.
Nominal variables have no defined order. Numerical values are assigned to represent individual items, for example,
marital status: 1 = married, 2 = divorced, 3 = single. The order (number assigned) has no meaning for a nominal
variable. Nominal data are reported as proportions (percentages and ratios).
Ordinal variables have an inherent order, for example, pain severity, 1 = no pain, ... 10 = worst pain ever. Ordinal
variables allow us to rank order individual items.
❍ What is a binary observation?
It is a nominal measure that has only two outcomes (eg, amenorrhea: yes or no)
❍ What is the difference between an explanatory/predictor variable and an outcome variable?
An explanatory/predictor variable is the independent variable and the outcome variable is the dependent variable in
a study. Qualitative or quantitative variables can be independent or dependent variables.