Statistics Lecture 1

Measurement

The process of comparing a value to a standard. Ex: distance, force, time, frequency

Data

The result of measurement

Statistics

A mathematical technique by which data are organized, treated, and presented for interpretation and evaluation

Reliability

Reproducibility and consistency

Validity

The soundness or the appropriateness of the test in measuring what it is designed to measure

Objectivity

Data is collected without bias

Variable

A characteristic of a person, place, or object that can assume more than one value

Constant

A characteristic that can assume only one value

Continuous variable

Theoretically can assume any value; value assumed is only limited by precision of measurement instrument

Discrete variable

Limited to certain numbers, usually whole numbers

Nominal scale

Data may only be classified

Ordinal scale

Data are ranked

Interval scale

Meaningful differences between values with no true zero point

Ratio scale

Meaningful zero point and ratio between values

Research

A systematic investigation, including research development, testing and evaluation, designed to develop or contribute to generalizable knowledge

Observational research

Describing events or conditions, which the researcher does not actively manipulate; examine correlations between variables

Experimental research

Research process that involves manipulating and controlling events or variables to solve a problem (actively involved)

Theory

A belief regarding a concept or a series of related concepts

Hypotheses

Testable, falsifiable; “burden of disproof”

Hypothesis

An educated guess or logical assumption that is based on prior research or known facts and that can be tested

Research hypothesis

The hypothesis that prompts the research; usually predicts relationships or differences between or among groups

Null hypothesis

Predicts no relationship or no difference between the groups

Independent variable

Variable that is manipulated or controlled by researcher

Dependent variable

That which is measured

Population

any group of persons, places, etc. that have at least one common characteristic

Sample

A certain fraction randomly selected from the population

P-value

The probability the result occurred by random chance

If p<0.05

We reject Ho

Step 1 of measurement

The object being measured is identified and defined

Step 2 of measurement

Selection of measurement standard

Step 3 of measurement

Comparison of object to the standard

Step 4 of measurement

Quantitative statement made

Example of nominal scale

Sex (M/F)

Example of ordinal scale

Pain scales (0-10) or Borg scale (6-20)

Example of interval scale

Temperature

Example of ratio scale

Height/Weight/Distance

Internal validity

Strength of experimental design/control of intervening variables

External validity

Generalize results from sample to population

Descriptive statistics

methods for organizing and summarizing data (table or graph)

Inferential statistics

methods for using sample data to make general conclusions about populations

Correlational study

used to determine whether there is a relationship between two variables and to describe the relationship; simply observes the two variables as they exist naturally