AP Psych Chapter 2

Empiricism

is the belief that accurate knowledge can be acquired through observation

Scientific method

is a procedure for using empirical evidence to establish facts 

Theories

is a hypothetical explanation of a natural phenomenon. Is explanation of how something in the natural world works and why it works that way 

Hypothesis 

is a falsifiable prediction made by a theory

Empirical method

is a set of rules and techniques for observation

Method

is technologies that enhance the power of senses

Methods of observation

determines what people do

Methods of explanation

determines why people do something 

Operational definition

a description of property in a measurable terms

Construct validity

the extent to which the thing being measured adequately characterizes the property

Power

a detector’s ability to detect the presence of differences or changes in the magnitude of a property 

Reliability 

a detector’s ability to detect the absence of differences or changes in the magnitude of a property 

Demand characteristics

those aspects of an observational setting that cause people to behave as they think someone else wants or expects them to

Naturalistic observation

a technique for gathering scientific information by unobtrusively observing people in their natural environments 

Observer bias

the tendency for observers’ expectations to influence both what they believe they observe and what they actually observed

Double-blind study

a study in which neither the researcher nor the participant knows how the participants are expected to behave

Population

a complete collection of people 

Sample

 a partial collection of people drawn from a population 

Frequency distribution

 a graphic representation showing the number of times that the measurement of a property takes on each of its possible values

Normal distribution 

 a mathematically defined distribution in which the frequency of measurements is highest in the middle and decreases symmetrically in both directions

Mode

the value of the most frequently observed measurement

Mean

the average value of all the measurements

Median

the value that is greater than or equal to half the measurements and less than or equal to half the measurements 

Descriptions of variability

statements about where the measurements in a frequency distribution tend to lie relative to each other

Range

the value of the largest measurement in a frequency distribution minus the value of the smallest measurement

Standard deviation

a statistic that describes how each of the measurements in a frequency distribution differs from the mean 

Variables

properties that can take on different values

Correlation 

the relationship that results when variations in the value of one variable are synchronized with variations in the value of the other 

Correlation coefficient

a mathematical measure of both the direction and strength of a correlation, which is symbolized by the letter r 

Natural correlations 

the correlations we observe in the world around us

Third-variable problem 

the fact that the natural correlation between two variables cannot be taken as evidence of a causal relationship between them because the third variable might be causing them both 

Experimentation

a technique for establishing the causal relationship between variables 

Manipulation

a technique for determining the causal power of a variable by actively changing its value 

Independent variable

the variable that is manipulated in an experiment 

Dependent variable

the variable that is measured in an experiment

Self-selection

a problem that occurs when anything about a participant determines the participant’s condition 

Random assignment

a procedure that assigns participants to a condition by change 

Internal validity

an attribute of an experiment that allows it to establish causal relationships

External validity 

an attribute that of an experiment in which variables have been operationally defined in a normal, typical or realistic way 

Case method

a procedure for gathering scientific information by studying a single individual 

Random sampling 

a technique for choosing participants that ensures that every member of a population has an equal change of being included in the sample

Replication

an experiment that uses the same procedures as a previous experiment but with a new sample from the same population 

Type 1 replication error

when researchers conclude that there is a causal relationship between two variables when in fact there is not 

Type 2 replication error

when researchers conclude that there is not a causal relationship between two variables when in fact there is 

Informed consent 

is a verbal agreement to participate in a study made by an adult who has been informed of all the risks that participation may entail

Debriefing

a verbal description of the true nature and purpose of a study