CH. 1: Introduction to Statistics

Statistics

the terms statistics refers to a set of mathematical procedures for organizing, summarizing, and interpreting information

Sample

a sample is a set of indivduals selected from a population, usually intended to represent the population in a research study

Random Sample

in a random sample everyone in the population has an equal chance of being selected

Variable

a characteristics or condition that changes or has different values for different indivdiuals

Datum

(singular) is a single measurement or observation and is commonly called a score or raw score

Data Set

a collection of measurements or observations

Data

(plural) are measurements or observations

Parameter

a value, usually a numerival value, that describes a population. a parameter is usually derived from measurements of the individuals in the population

Statistic

a value, usually a numerical vaue, that describes a sample. a statistic is usually derived from measurements of the indivduals in the sample

Descriptive Statistics

are statistical procedures used to summarize, organize, and simplify data

Inferential Statistics

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

Sampling Error

the naturally occurring discrepancy, or error, that exists between a sample statistic and the corresponding population parameter

Constructs

are internal attributes or charactersitics that cannot be directly observed but are useful for describing and explaining behavior ex. motivatoin, anxiety, hunger

Operational Definition

identifies a measurement procedure (a set of operations) for measuring an external beahvior and uses the resulting measurements as a definition and a measurement of a hypothetical construct

Discrete Variable

consists of separate, indivisible categories. no values can exist between two neighboring categories

Continuous

for a continuous variable, there are an infinite number of possible values that fall between any two observed values. a continuous variable is divisible into an infinite number of fractional parts

Real Limits

are the boundaries of intervals for scores that are represented on a continuous number line. the real limit separating two adjacent scores is located exactly halfway between the scores. each score has two real limits

Lower Real Limit

the upper real limit is at the top of the interval, and the lower real limit is at the bottom

Upper Real Limit

the upper real limit is at the top of the interval, and the lower real limit is at the bottom

Nominal

a nominal scale consists of a set of categories that have different names. measurements on a nominal scale label and categorize observations, but do not make any quantitative distinctions between observations

Ordinal Scale

an ordinal scale consists or a set of categories that are organized in an ordered sequence. meausrements on an ordinal scale rank observations in terms of size or magnitude

Interval Scale

consists of ordered categories that are all intervals of exactly the same size. equal differences between numbers on a scale reflect equal differences in magnitude. however, the zero point on a interval scale is arbitrary and does not indicate a zero amount of the variable being measured

Ratio Scale

is an interval scale with the additional feautre of an asbolute zero point. with a ratio scale, ratios of numbers do reflect ratios of magnitude

Descriptive Research

descriptive research or the descriptive research strategy involves measuring one or more separate variables for each individual with the intent of simply describing the individual variables

Correlational Method or Correlational Research Strategy

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

Data Structure 1

one group with one or more separate variables measured for each indivdual: descriptive research

Data Structure 2

one group with two variables measured for each individual: the correlational method

Data Structure 3

comparing two (or more) groups of scores: experimental and nonexperimental methods

Experimental Method

in the experimental method, one variable is manipulated while another variable is observed and measured. to establish a cause-and-effect relationship between the two variables, an experiment attempts to control all other variables to prevent them from influencing the results (aka the experimental research strategy)

Individual Differences

the individuals in a research study differ on a variety of particpants variables such as age, weight, skills, motivation, and personality. the differences from one participant to another are known as individual differences

Independent Variable

the variable that is manipulated by the researcher. in behavioral research, the independent variable usually consists of the two (or more) treatment conditions to which subjects are exposed. the indepndent variable is manipulated piror to observing the dependent variable

Dependent Variable

the dependent varaible is the one that is observed to assess the effect of the treatment. the dependent variable is the variable that is measured in the experiment and its value changes in a way taht depends on the status of the independent variable

Control Condition

individuals in a control condition do not receive the experimental treatment. instead, they either receive no treatment or they receive a neutral, placebo treatment. the purpose of a control conditions is to provide a baseline for comparison with the experimental condition

Experimental Condition

individuals in the experimental condition do receive the experimental treatment

Quasi-Independent Variable

in a nonexperimental study, the “independent variable” that is used to create the different groups of scores is often called the quasi-independent variable