Variable
Basic unit of statistics; must take on more than one value and be measurable
Discreet variable. What does it measure?
Variables that have a minimum unit of measurement that CANNOT be subdivided
Continuous variable. What can it measure?
Variables that can take on all numerical values in an interval
Nominal-level variable
It's values CANNOT be ranked in any meaningful way
Ordinal-level variable
It's values CAN be ranked but the difference between the categories cannot be measured
Interval/ratio-level variable
It's values CAN be ranked and the differences CAN be measured definitively
Descriptive data
Complete data on a population, NO estimations or guessing needed
Inferential data
Incomplete data on a population, inferred onto a population to make an ESTIMATED guess
Frequency (f)
The number of times a given observation appears in a data set.
Frequency distribution
A table that organizes how many observations fall into each category or interval of a variable
Cumulative frequency distribution
The number of observations that are at or below each category or interval of a given variable
Cumulative percent distribution
The percentage of observations that are at or below each category or interval of a given variable
Central tendency
The most common value or middle value in the distribution of observations of a given variable
Mode
The category with the greatest frequency or percentage of observations, not the frequency value itself
Median
The middle most value in the distribution of observations of a given variable
Mean
The most 'average' or likely observation in the distribution of a given variable
Percentile
A specific type of measurement that represents what percentage of the distribution falls BELOW a specific score
Positively skewed distribution
A distribution with a handful of extremely large values. The mean > median
Negatively skewed distribution
A distribution with a handful of extremely low values. The mean < median
Measures of variability
The diversity or dispersion in the distribution of observations of a given variable
Range
The difference between the lowest and highest scores in a data set.
Interquartile range (IQR)
The difference between the 25th and 75th percentile
Variance
The difference between each observation and the mean of distribution of the observations
Standard deviation
The square root of the variance, reverts data back to it's original metric
Independent Variable (IV)
The CAUSE and variable that can be changed
Dependent Variable (DV)
The EFFECT that's dependent on the cause
Population
Every single member of a group of interest
Sample
Small subset of an entire group of interest
Raw Frequency
All given information in a set of data, plain number of observations in each category
Relative frequency
Percentage representing the number of observations in a category relative to other categories