# Shared Flashcard Set

## Details

POLI stat
intro to statistics
36
Political Studies
02/26/2009

Term
 Reliability
Definition
 the extent to which a measure is repeatable or consistent. If it is reliable, repeating that same measure on the same case/observation will yield the same values for the variabler=t/(t+e)
Term
 observed score
Definition
 =true score + errorx=t+e
Term
 tests of reliablitiy
Definition
 test retest--perform the same test multiple timesalternative form--same test/concept, different implementation/method and different time, reliability assesed by correlationIntercoder Reliability--different observer using the same measure
Term
 validity
Definition
 a valid measure accurately represents the concept it is trying to measure. an invalid measure measures something else than what was intended
Term
 types of validity
Definition
 face validity, content validityconstruct validity
Term
 face validity
Definition
 seems like a valid way to measure a concept on the face value
Term
 content reliability
Definition
 the amount to which a measure represents/addresses all faces of a concept
Term
 construct reliability
Definition
 the amount to which it is related to other measures that it is required to be related to.
Term
 test retest
Definition
 test retest--perform the same test multiple times
Term
 alternative form
Definition
 alternative form--same test/concept, different implementation/method and different time, reliability assesed by correlation
Term
 Intercoder Reliability
Definition
 Intercoder Reliability--different observer using the same measure
Term
 critical steps
Definition
 1. clear goal2. reliable and valid measure3. comparaility4. know your data
Term
 hypotheses
Definition
 characterisits, general and specific, declarative form, abt expected relationship, brief, direct, guided by a theory
Term
 skewness
Definition
 measures symmetry,not skewed: cases tend to cluster symmetrically around the mean and taper off evenlyskewed: one tail is longer and skinnier, affects mean not median
Term
 positive skew
Definition
 right tail is longer and skinnier, pulls mean upward
Term
 negative skew
Definition
 left tail is longer and skinnier, pulls mean downward
Term
 types of variables
Definition
 1. categorical2. ordinal3. continuous
Term
 categorical variable
Definition
 variables are clearly defined in seperate categories. cannot rank and there is no natural order
Term
 ordinal variable
Definition
 varaibles are clearly defined. you can rank. not equal unit differencesex. political identificationleft independent right
Term
 continuous variable
Definition
 variables clearly defined, can rank, equal unit differences ex. annual income
Term
 descriptive statistics
Definition
 organize and summarize datafrequencies, porportions, percents, ratios, rates
Term
 central tendency
Definition
 estimation of the center of a distribution of values, can use mean or median
Term
 rank statistics
Definition
 can be presented using a box and whisker plot
Term
 variance
Definition
 how spread out a distribution is var(y)= s^2(y)={the sum of (yi- average y)^2} /[n-1]
Term
 mean
Definition
 average(sum of Yi)/n"expected value"
Term
 standard deviation
Definition
 more accurate measure of the distribtion, measures how far an observation is from the mean. average difference between each of our cases and the meanst dev= s(y)= square root of variance= square root of [(sum yi-mean y)^2/n-1]
Term
 zero sum property
Definition
 sum (yi- mean 7)=0the sum of (all variables of y minus the mean) is equal to zero
Term
 least square property
Definition
 the sum of (yi-mean y)^2 < the sum of (yi-c)^2 when c doesnt equal the mean of y
Term
 sample
Definition
 subset of the population
Term
 central limit theorem
Definition
 regardless of the distribution, the expected value(mean) for the sample will be normally distributed around the population expected value (mean)
Term
 normal distribution
Definition
 skewness=0 kurtosis=0mean=median=mode1 st dev=68% of data2 st dev=95% of data3 st dev=99.7% of data
Term
 kurtosis
Definition
 indicates the steepness of the statistical distributionpositive=very steepnegative=not steep, flatter
Term
 4 hurdles
Definition
 1. credible causal mechanism?2. could y cause x?3. covariation?4. confounding variable z?
Term