RDA Week 4: Statistical Evaluation of Data

The Role of Statistics

-Help organize and summarize data

-Help answer the general questions that initiated the research

Descriptive Statistics

Methods that help researchers organize, summarize, and simplify results from a research study

Inferential Statistics

Methods that use results obtained from samples to help make generalizations about populations

A Population

The entire set of individuals of interest to a researcher; known as the target population or the group in which study results can be extrapolated to

A Sample

A group of individuals selected from a population intended to represent the population in a research study

A Parameter

Refers to a summary value that describes a population

A Statistic

Refers to a summary value that describes a sample

Frequency Distributions

A method of simplifying and organizing a set of scores by grouping them into an organized display

Frequency Distribution Setup

-First column = the scale of measurement (categories or bins)

-Second column = the frequency of individuals (or data points) in each category

A Histogram

Displays a bar above each score so that the height of the bar indicates the frequency of occurrence for the given score

-Interval/Ratio

-Bars touch

A Polygon

Displays a point above each score so that the height of the point indicates the frequency of occurrence for the given score

-Interval/Ratio

-Line touches the X-axis

A Bar Graph

Displays a bar above each score so that the height of the bar indicates the frequency of occurrence for the group category

-Nominal/Ordinal

-Bars don’t touch

Central Tendency

A statistical measure that identifies a single score to define as the center of a distribution; the value that is most typical or representative of the group

Mean

The mathematical average of the scores

Median

The score that divides a distribution in half

Mode

The most commonly occurring score

Nominal and Ordinal Scales (Categorical)

Percentages (0-100%)

Proportions (0.0-1.0)