Statistics
a collection of procedures and principles for gathering data and analyzing information to help people make decisions when faced with uncertainty
Data
plural word referring to numbers or non-numerical labels collected from a set of entities
Median
value in the middle when the numbers are put in order. For an even number of entities, the median is the average of the middle two values.
Lower Quartile and Upper Quartile
roughly, the medians of the lower and upper halves of the ordered data
Rate
the number of times it occurs per number of opportunities for it to occur
Risk
can be estimated using the past rate for that outcome, if it is assumed the future will be like the past.
Base rate or baseline risk
rate or risk at a beginning time period or under specific conditions
population
a collection of all individuals abut which information is desired
random sample
a subset of the population selected so that every individual has a specified probability of being part of the sample
poll or sample survey
investigators gather opinions or other information from each individual included int he sample
margin of error
number that is added to and subtracted from the sample information to produce and interval that is 95% certain to contain the true value for the population
margin of sampling error
to distinguish it form other sources of errors and biases that can distort the results
nonparticipation bias
many people who are selected for the sample either do not respond at all or do not respond to some of the key survey questions
self-selected sample or volunteer sample
sample that tells you nothing about the larger population at all
observational study
participants are merely observed and measured
variable
a characteristic that differs from one individual to the next. it may be numerical or categorical
confounding variable
not the main concern of the study but may be partially responsible for the observed results
randomized experiment
a study in which treatments are randomly assigned to participants
treatment
specific regimen or procedure assigned to participants by the experimenter
random assignment
each participant has a specified probability of being assigned to each treatment
placebo
a pill or treatment designed to look just like the active treatment but with no active ingredients
statistically significant relationship
one that is large enough to be unlikely to have occurred in the sample if there was no relationship or difference in the population
practitcal significance or practical importance
differences in group means are not likely due to sampling error
random assignment
each participant has a specified probability of being assigned to each treatment
placebo
a pill or treatment designed to look just like the active treatment but with no active ingredients