quantative methods in psych ch 1

statistics

a set of procedures for organizing, summarizing, and interpreting information

helps us get a sense of a large quantitive of info

organizing stats

collecting and examining all info

summarizing stats

representing info: reducing all info to single values and describing different characteristics

interpreting stats

comparing summarized info

more complicated manipulations and calculations

what can stats be used for?

to help answer research questions using dta

population

the set of all individuals of interest in a particular study

sample

a set of individuals who are selected from a population

• smaller than the population

• our best representation of the population

• results must generalize to the population

parameter

value that describes a population

derived from measurements of individuals in the population

statistic

value that describes a sample

derived from measurements of individuals in the sample

sampling error

natural discrepancy or error between a parameter and a statistic

stats do not represent parameters

descriptive statistics

used t summarize, organize, and simplify data

interferential statistics

methods for using sample datat to make general conclusions about populations

definign or sampling an error

variable

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

data

measurements or observations

data set

a collection of measurements or observations

constructs

internal attributes or characteristics that cannot be directly observed

operational definitions

external behaviors that can be observed and measured that define the construct

discrete variable

separate and indivisible categories

no values between categories

continuous variables

infinite number of possible values

what are the scales of measurement?

nominal, ordinal, interval, ratio

nominal scale

a set of categories with names

no quantative differences

ordinal scale

categories in an ordered sequence

ranked in terms of magnitude or size

no indication of “how much” of a difference

interval scale

ordered categories

intervals are the same size between categories

no meaningful zero

ratio zero

interval scalle with a meaningful zero

correlational method

determine the relationship between different observed variables

correlation does not equal causation

manipulation

one variable is manipulated while another variable is observed and measured

control

all other extraneous variables are controlled

establishment of a cause and effect relationship between the IV and DV

control condition

does not receive the experimental treatment

provides a baseline

experimental condition

receives the experimental treatment

nonequivalent group

pre-existing groups that we can’t control

pre-post studies

compare pre-experiment and post-experiment

just one group with two sets of scores

mathematical review

uses Appendix A

statistical notation

what are X or Y stand for?

individual scores

number of scores in a population

N

number of scores in the sample

n

what does Σ stand for?

summation symbol

followed by a symbol or equation that defines what is to be added up

the order of mathematical operations

parentheses done first

raising to exponents is done second

multiplying and/or dividing goes third

summation is done next

any other addition or subtraction is done