Descriptive Statistics

Qualitative (Categorical)

Measures of types and may be represented by a name, symbol or number code "What type" of "which category"

Quantative (Numerical)

Measures of values/counts are expressed as numbers Relates to qauntity of something, "how many" or "how much:

Absolute Measure

Measures variability in term os same uints

Discrete Data

Numerical data values that can be COUNTED & LISTED, cannot be broken into smaller pieces.

Continous Data

Numerical data values that cannot be COUNTED or LISTED, can be broken down into smaller parts

Incidence

Occurence of NEW cases of disease or injury a population over a specified period of time Incidence proportion: Proportion of an initially disease-free population that develops disease Incidence rate: Measures of incidence that incoporates time directly

Interquartile Range

The data that contains the middle 50%

Range

The difference between the largest and smallest value in a set

Standard Deviation

The amount we expect to deviate away from the mean value Square root of the "variance"

Prevalence Fomula

# EXISTING cases at time point/ # in TOTAL POPULATION at time point

Measures of Central Tendency

A value that describes a set of data by describing the central position of that data.

Variance

Average of square deviations Mean of data points, subtracting the mean from each data point individually, squaring THESE results How much individuals data points differ from the average (mean) of that data Spread out or scattered that data is

Ordinal Data

Classifies variables into categories which have a natural order or rank.

Statistics

Collection, organization, & interpretation of data

Nominal Data

Divides variables into mutually exclusive, labeled categories

Inferential Statistics

Drawing conclusions about that population based on the date collected

Weighted Mean

Each value is equally as important and carries the same weight in the equation

Dispersion

How a similar a set of scores MORE similar scores, LOWER the measure of dispersion LESS similar scores, MORE the measure of disperson

Comparison: Prevalance & Incidence

PREVELANCE Existing Disease (new and old cases) Denominator: whole population Does require follow up Depends on the duration of the illness Preferred measure when assessing burden of disease INCIDENCE New Disease (new cases only) Denominator: Population at risk Requires follow up to identify new cases Does not depend on the duration of the illness Preferred for studying etiology

Prevalence

Proportion of persons in a population, who have a particular disease or attribute at a specified point in time Point prevalence: prevalence measured at a particular point in time Period prevalence: prevalence measured over an interval of time

Descriptive Statistics

Summarizing/organizing the data related to the characteristics of the sample

Skewness

Symmetry in the distribution of SCORES. Skewed to RIGHT: positive Skewed to LEFT: negative

Relative Measure

Vairability of two or more data that are independent of the units of measurement

Quartiles

Values that divide a data set into four equal parts