Lecture 1 – Recap
1. Methodology
Variables
− observable or hypothetical events that can change and whose changes can be measured in
some way
− independent variables – explanatory variables
− manipulated variable controlled by experimenter
− predictor
− dependent variables – response variables
− observed effect
− outcome
,− extraneous variables
− variables that are not of interest to the researcher but that might influence the
variables of interest if not controlled
− variables that provide alternative explanation
− if not controlled -> confounding variable
Variables: levels of measurement
− nominal – variable represents a category without logical order
− if there’s only 2 categories – dichotomous
− e.g., What is your sex? (female vs. male)
− e.g., What is your favorite color? (red vs. blue vs. ...)
− e.g., What type of respiratory disease do you have? (Asthma vs. COPD vs.
emphysema vs. ...)
− ordinal – ranked variable, represents a category with a specific order or rank position
− e.g., What is your position in the race? (1st, 2nd, last...)
− e.g., What is your position in height ranking? (tallest, shortest,..)
− e.g., How good is your lung function? (horrible, bad, reasonable, good, excellent)
− discrete – counts, finite values
− e.g., How many times does the rat push the lever?
− e.g., How many times per week do you go to the grocery store?
− e.g., How many times do you cough?
− continuous – scale variable with infinite values
− e.g., How much does this package weigh?
− e.g., What is the distance between you and the blackboard?
− e.g., What is your lung volume in liters?
,Research design
− research question
− causal effect or association
− dependent variables
− measurement
− type (nominal, ordinal, discrete, continuous)
− number of variables
− independent variables
− measurement
− type (nominal, ordinal, discrete, continuous)
− number of variables
− manipulation
− compare groups or conditions, the number of
− Are measurements/manipulations dependent/within-subjects/paired or
independent/between-subjects/not paired?
, − cross-sectional design – a type of research design in which you collect data from many
different individuals at a single point in time
− in cross-sectional research, the variables are observed without influencing them
− case control design – a study that compares patients who have a disease or outcome of
interest (cases) with patients who do not have the disease or outcome (controls), and looks
back retrospectively to compare how frequently the exposure to a risk factor is present in
each group to determine the relationship between the risk factor and the disease
− no intervention is attempted, and no attempt is made to alter the course of the
disease
− cohort design – a type of research design that follow groups of people over time
− a particular form of longitudinal study that samples a cohort, performing a cross-
section at intervals through time
− randomized control design – a study design that randomly assigns participants into an
experimental group or a control group
− as the study is conducted, the only expected difference between the control and
experimental groups in a randomized controlled trial (RCT) is the outcome variable
being studied
− cross-over design – a longitudinal study in which subjects receive a sequence of different
treatments
− 2 or more interventions are assessed
