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Statistics

The science of conducting studies to collect, organize, summarize, analyze, and draw conclusions from data

Variable

A characteristic or attribute that can assume different values

Random Variable

Variables whose values are determined by chance

Data

The values (measurement or observations) that the variables can assume

Data Set

A collection of data values

Data Value or Datum

Each value in the data set

Descriptive Statistics

Consists of the collection, organization, summarization, and presentation of data

Inferential Statistics

Consists of generalizing from samples to population, performing estimations and hypotheses tests, determining relationships among variables and making predictions; uses probability

Probability

Likelihood that a particular event will ocucur

Population

Consists of all subjects (human or otherwise) that are being studied

Sample

A group fo subjects selected from a population

Hypothesis Testing

A decision-making process for evaluating claims about a population, based on information obtained from samples

Qualitative Values

Variables that can be placed into distinct categories, according to some characteristic or attribute

Quantitative Values

Numerical and can be ordered or ranked

Discrete Variables

They assume values that can be counted

Continuous Variables

Can assume an infinite number of values between any two specific values. They are obtained by measuring. THey often include fractions and decimals

Nominal Level of Measurement

Classifies data into mutually exclusive (non-overlapping), exhausting categories in which no order or ranking can be imposed on the data
Categorical (names)

Ordinal Level of Measurement

Classifies data into categories that can be ranked; however, precise differences between the ranks do not exist
Nominal, plus can be ranked (order)

Interval Level of Measurement

Ranks data, and precise differences between units of measure do exist; however, there is no meaningful zero
Ordinal, plus intervals are consistent

Ratio Level of Measurement

Possesses all the characteristics of interval measurement, and there exists a true zero. In addition, true ratios exist when the same variable is measured on two different members of the population
Interval, plus ratios are consistent, true zero

Random Sample

Subjects are selected by random numbers

Systematic Sample

Subjects are selected by using kth number after the first subject is randomly selected from 1 through k

Stratified Sample

Subjects are selected by dividing up the population into groups (strata), and subjects are randomly selected within groups

Cluster Sample

Subjects are selected by using an intact group that is representative of the population

Convenient Sample

Subjects are selected by convenience

Observational Study

The researchers observe what is happening or what has happened in the past and tries to draw conclusions

Experimental Study

The researcher manipulates one of the variables and tries to determine how the manipulation influences other variables

Quasi-Experimental Study

Researchers use intact groups; these are done in education where intact groups are available in the form of existing classrooms

Independent Variable/Explanatory Variable

The variable that is being manipulated

Dependent Variable/Outcome Variable

The variable that is studied to see if it has changed significantly due to the manipulation of the independent variable

Treatment Group

In a study, this group receives special instruction

Control Group

Unlike the Treatment Group, in a study the Control Group does not receive special instruction

Hawthorne Effect

A change in a subject's behavior caused simply by the awareness of being studied

Confounding Variable

Variable that influences the dependent variable but was not separated from the independent variable