Week 2 Flashcards
To learn the concepts and terms of week 2's class
Variable
A variable is any observable feature of the natural world
DATUM
A datum, or observation, is any one record of the state of a variable.
DATASET
Any collection of observations made on a variable is a data set
POPULATION
The set of all possible observations on a variable is the population
FINITE
POPULATION
Populations can be either finite or infinite. Finite populations have a finite, countable
number of elements and can, in theory at least, be completely sampled.
INFINITE
POPULATION
Infinite populations have an infinite number of elements and can never be completely
sampled.
SAMPLE
Large and infinite populations cannot be observed in their entirety, so we take only
(nearly always randomly) a sample (sub)set of observations from a population.
PARAMETER
A parameter is some characteristic of the distribution of the values of a variable in a
population.
STATISTIC
The term “statistic” is used in two ways: to refer to the entire body of procedures for
dealing with data; or to refer to estimates of population parameters based on samples.
Mode
most common value
Median
middle value
Mean
average value
Sample mean symbol
⨱
Population mean symbol
μ
Variance
spread of distribution
Skewness
skew of peak distribution to one side of the mean
Kurtosis
peakedness or flatness of distribution
VARIANCE (s2
measures the dispersion of data around their
mean value
NORMAL DISTRIBUTION
a symmetric distribution, often called a
bell-curve which describes many parameters of the natural world,
e.g. height, weight, test scores in a very large class
STANDARD DEVIATION
a measure of dispersion in the
data, standardised relative to the mean
SKEWNESS
measures the extent to which the distribution is
“pushed” to either side of the mean
Mesokurtic
meso – middle, intermediate, halfway
Leptokurtic
lepto – small, fine, thin, delicate
Platykurtic
platy – broad, flat
NOMINAL/CLASSIFICATION variables
variables can be classified into named groups
e.g. sex, colour, habitat type etc.
ORDINAL/RANKING variables
can be ranked in order e.g. social position,
size-class, education level etc.
NUMERICAL/QUANTITATIVE variables
can be enumerated or quantified
(counted or measured), e.g. height, weight etc
