PsychStats- Chapter 1: Introduction to Statistics

PsychStats- Chapter 1: Introduction to Statistics

Statistics

refers to a set of mathematical procedures for organizing, summarizing and interpreting information.

Population

is the set of all individuals of interest in a particular study

Sample

a set of individuals selected from a population, usually intended to represent the population in a research study.

Variable

a characteristic or condition that changes or has different values for different individuals

Data

Facts and statistics collected together for reference or analysis

statistic value

Value that describes the sample. Taken from measurements of the sample

Taken from measurements of the sample

descriptive statistics

statistics that summarize the data collected in a study

inferential statistics

consists of techniques that allow us to study samples and then make generalizations about the populations from which they were selected.

sampling error

an error that occurs when a sample somehow does not represent the target population

Individual Variables: Descriptive Research

research studies conducted simply to describe individual variables as they exist naturally.

correlational method

two different variables are observed to determine whether there is a relationship between them

Limitations

The results from the Correlation study can demonstrate the existence of a relationship between two variables, but they do not provide an explanation for the relationship.

experimental method of research

A method of investigation used to demonstrate cause-and-effect relationships by purposely manipulating one factor thought to produce change in another factor.

2 characteristics of Experimental Method of Research:

1. Manipulation

2. Control

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2 general categories of variables that researchers must consider:

1. Participant variables

2. Environmental Variables

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Participant variables

characteristics such as age, gender, and intelligence that vary from one individual to another

environmental variables

characteristics of the environment such as lighting, time of day, and weather conditions

Nonexperimental Methods: Non-equivalent Groups and Post Studies

Non-experimental method is when the 2 characteristics of an experimental method is not met or set. Groups are nonequivalent when the participant and environmental variables are not the same within a group or between groups

Control Condition

the no-treatment condition.

experimental condition

the condition of an experiment that exposes participants to the treatment, that is, to one version of the independent variable (treatment condition)

dependent variable

The outcome factor; the variable that may change in response to manipulations of the independent variable.

quasi-independent variable

in a non-experimental study, the "independent variable" that is used to create the different groups of scores

discrete variable

Consists of separate, indivisible categories. No values can exist between two neighboring categories.

continuous variable

a quantitative variable that has an infinite number of possible values that are not countable

scales of measurement

1. Nominal, Ordinal, Interval, Ratio

Nominal scale of measurement

Used when data can be organized into categories of a defined property but the categories cannot be rank ordered.

ordinal scale of measurement

Data are assigned to categories that can be ranked.

interval scale of measurement

This type of measurement uses interval scales, which have equal numerical distances between intervals.

ratio scale of measurement

All of the same in interval, except there is the addition of a true-zero point. Ex. height, weight, time on task, income, age

greek letter sigma

is used to stand for summation

Order of mathematical operations

1. parentheses

2. Squaring

3. Multiplying and/or dividing, left to right

4. Summation (sigma)

5. Addition and/or subtraction, left to right