stats i definitions

sample

a subset of the population of interest

selection bias

a systematic fault in a method that will typically lead to a wrong answer

representative

the qualities/attributes of the sample reflect those of the entire population of interest

endogenous factors (coin flip)

factors that are latent to the coin itself which influence the outcome of coin flip

exogenous factors (coin flip)

factors that are external to the coin that will affect the outcome of the coin flip

descriptive statistics

summarize data by describing what was observed numerically or graphically

inferential statistics

uses patterns in the data to draw conclusions about the population of interest, accounting for randomness

experimental unit

a single entity or element, usually a person, object or an event, whose characteristics are of interest

statistical/target population

the collection or set of experimental units whose properties are to be analyzed

sample

a set of experimental units, usually derived from a statistical population as a subset of the population

variable

a characteristic of interest about each individual element of a statistical population or sample

data (singular)

the manifestation of the variable/s associated with one element of a population or sample. This can be a number, a word, or a symbol

data (plural)

the set of values collected for the variables from each of the elements belonging to the sample

qualitative or categorical

a variable that categorizes or describes a characteristic of an element, usually with a word
- subdivided into two scales: nominal then ordinal

qualitative or numerical

a variable that quantifies a characteristic of an element, that is a number is attributed to the element
- subdivided into two scales: interval then ratio
- numerical variables from either scale can be discrete or continuous

nominal scale

a qualitative variable in which there is no ordering to its categories
- e.g. race, religion, occupation, state

ordinal scale

a qualitative variable in which there is some ordering to its categories, but they themselves, nor any differences between them are quantifiable
e.g. education level, military rank

interval scale

a variable that not only is described by a number, but also the difference between values have meaningful interpretations

ratio scale

a variable that is not only on the interval scale (i.e. can be described via a number with quantifiable differences) but there also exists a ‘true zero’ (i.e. a meaningful, unique and non-arbitrary value that is a reference/starting point) so that multiplicative statements (such as constructing a ratio) are meaningful

discrete variable

a quantitative variable whose set of possible values is either finite or else can be listed in an infinite sequence

continuous variable

a quantitative variable whose set of possible values consists of an entire interval on the number line (or the whole number line)