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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
