Chapter 13 Statistics - Organising the Data Flashcards
Raw data/scores
Untreated, uncovered values obtained directly from measuring process used in a study
Categorical Variable
Variable where cases are merely placed into independent, separate categories
Measured Variable
Variable where cases measured on it are placed on some sort of scale that has direction
Levels of Measurement
Levels at which data are categorised or measured
Nominal
Level of measurement at which numbers are only labels for categories
Ordinal
Level of measurement at which cases are arranged in rank positions
Interval
Level of measurement at which each unit on a scale represents an equal change in the variable measured
Coding
Giving ‘dummy’ numbers to discrete levels of an independent variable
Frequency data/frequencies
Numbers of cases in specific categories
Quasi-Interval Scale
Scale that appears to be interval by where equal intervals do not necessarily measure equal amounts of the construct
Ratio Scale
Interval-type scale where proportions on the scale are meaningful; usually an absolute zero exists
Median Split Method
Dividing a set of measured values into two groups by dividing them into high and low at their median
Continuous Scale/Variable
Scale where there are no discrete steps; theoretically, all points along the scale are meaningful
Discrete Scale/Variable
Scale on which not all subdivisions are meaningful; often one where the underlying construct to be measured can only come in whole units (e.g. number of children)
Data Set
Group of data points or values which can be summarised or analysed
Central Tendency
Formal term for any measure of the typical or middle value in a group
Dispersion
Technical and general term for any measure of the spread of values in a sample of data or population
Mean (arithmetic)
Average of values found by adding them all and dividing by the number of values in the set
Outliers
‘Rogue’ values at an extreme distance from the centre of the data set. Can be removed from analysis of data set because they unnecessarily distort statistics but this procedure must be openly reported.
Trimmed Mean
The mean of a data set with its most extreme 5% of values removed
Median
Measure of central tendency; middle value of data set
Median position/location
Position where median is to be found in an ordered data set
Class Intervals
Categories into which a continuous data scale can be divided in order to summarise frequencies
Mode/Modal Value
Measure of central tendency - most frequent value in a data set
Bi-modal Distribution
Data set with two modes
Range
Measure of dispersion - top to bottom value (plus one)
Interquartile Range
Distance between first and third quartile in a distribution
Semi-Interquartile Range
Half the distance between first and third quartile in a distribution
Deviation Score/Value
Amount by which a particular score differs from the mean of its set
Mean Deviation
Measure of dispersion - mean of all absolute deviations
Variance
Measure of dispersion - square of standard deviation
Standard Deviation
Measure of dispersion - the square root of the sum of all squared deviations from the mean divided by N or N-1
Uncorrected (SD)
Version of standard deviation or variance that is used if only wanting summary statistics for the group and not making population estimates (uses N as denominator)
Unbiased Estimate (of SD)
Version of standard deviation or variance that is used for population estimates (uses N-1 as denominator)
Degrees of Freedom
Common term in statistical analysis having to do with the number of individual data points that are free to vary given that overall summary values are known
Variation Ratio
Measure of dispersion - proportion of non-modal values to all values
Sample Statistic
Statistical measure of a sample (e.g. mean, standard deviation)
Population Parameter
Statistical measure of a population (e.g. mean, standard deviation)
