population

set of all individuals of interest in a study population = parameter

parameter

numerical value that describes a population can be a single measurement or set of measurements

sample

set of individuals selected from a population, representative of population in a study sample = statistic

statistics

numerical value that describes a sample can be a single measurement or set of measurements

descriptive statistic

statistical procedures that are used to summarize, organize, simplify data - make raw score meaningful e.g. mean, median, mode

inferential statistics

techniques that allow us to study samples then make generalizations about the population - infer sample -> population

sampling error

discrepancy/ amount of error that exists between a sample statistic and population parameter - important to consider in inferential statistics

construct

internal attributes/ characteristics that cannot be directly observed but are useful for describing and explaining behavior - hypothetical e.g happiness

operational definition

defines construct in terms of observable behaviors e.g. intelligence defines as performance on IQ test

nominal scale

categorical organization - can only measure qualitative difference e.g gender, country of origin, hair color

ordinal scale

categories organized in a certain sequence, differences are quantitative - amount between one person and next is not consistent e.g. class rank, rating scale

interval scale

ordered categories that are intervals of exactly same size with an arbitrary zero point - 0 does not mean the absence of the construct being measured e.g. celsius scale, temp

ratio scale

interval scale with absolute zero point - can describe differences between categories in terms of ratios (one thing is 3 times larger than another) e.g. weight, height, speed

discrete variables

separate, indivisible categories - whole numbers or specific categories - no decimals e.g 3 goals scores

continuous variables

infinite number of possible values that fall between any two observed values - divisible into infinite number of fractional parts e.g. height

real limits

boundaries of intervals for scores that are represented on a continuous number line - each score has two limits, half way between scores (upper real limit, lower real limit) e.g. if you have observed value of 8, actually represents range from 7.5 - 8.5 (kind of like rounding)

correlational method

two variables observed to see if there is a relationship between the two

experimental method

establishes cause and effect relationship between variables - must manipulate one variable, observe second - controlled research situation

non-experimental method

variable determines group (those that have depression) - don't manipulate

independent variable

manipulated variable - 2+ treatment conditions

dependent variable

observed for changes to assess effect

control

does not receive manipulated experimental treatment, baseline for comparison

quasi-independent variable

groups not created by manipulating independent variable - participent variable (male/female) - time variable (before/after)

summation notation

a way to represent scores n ∑ xi i = 1 i = the starting point of the scores n = the stopping point

µ

population mean

x

sample mean

σ

population standard deviation

s

sample standard deviation

σ2

population variance

s2

sample variance

SS/n (df w/ sample)