Exam 3b - 1 In an observational study you are not giving...

1. In an observational study you are not giving the subjects any type of treatment;
you are just recording what you observe. In an experiment, you are giving the
subjects a treatment and observing the effects of that treatment.
2. A retrospective study is an observational study in which you look at past data.
Typically used when you are studying something that is unethical (such as
drinking during pregnancy). A prospective study is an observational study in
which you observe over a significant period of time. This is used when you want
to study long term effects.
3. retrospective studies are usually unable to reach cause-and-effect conclusions. For
example, we cannot conclude that physiotherapy definitively improves RTW
outcomes among back-injured workers. This is because of confounding factors.
4. Considered the gold standard of study design, are prospective studies. They can
provide evidence of cause-and-effect relationships and support changes in clinical
practice or workplace interventions. In a randomized controlled trial, subjects are
randomly assigned to receive the intervention or control treatment, and outcomes
are evaluated after the intervention period.
5. Definitions
a. Control: An experiment that isolates the effect of one variable on a
system by holding constant all variables but the one under observation.
b. Replicate: is the repetition of an experimental condition so that the
variability associated with the phenomenon can be estimated.
c. Randomize: is the process of making something random; this means:
i. Generating a random permutation of a sequence (such as when
shuffling cards).
ii. Selecting a random sample of a population (important in statistical
sampling).
iii. Generating random numbers: see Random number generation.
iv. Transforming a data stream (such as when using a scrambler in
telecommunications).
d. Block: is the arranging of experimental units in groups (blocks) that are
similar to one another. For example, an experiment is designed to test a
new drug on patients. There are two levels of the treatment, drug , and
placebo , administered to male and female patients in a double blind trial.
The sex of the patient is a blocking factor accounting for treatment
variability between males and females .