Lec 6 Flashcards
what are goodness of fit tests?
are methods for comparing an observed frequency distributions against an expected frequency distribution.
what is a proportional model?
where the frequency of occurence of events is proportionate to opportunities.
a more generalized version of a proportional model is what?
a chi squared test
what is the formula for chi squared?
Xsquared=E(observed-expected)squared/expected
the P value is telling us what in relation to chi squared?
the chance of getting a greater x squared value
in our chi squared test we must compare the chi squared to a particular degree of freedom, what is a degree of freedom?
number of categories - 1 - the number of estimated perimeters of the data
a distribution of a chi-square test statistic is close to a chi squared distribution, what are the rules for that distribution?
no categories have a frequency less than 1, no more than 20% of the categories should have expected frequencies less than 5
what models are used to estimate expected frequencies?
the proportional model, theoretical model, utilizing binomial distribution, use the poission to calculate expected frequencies.
what is possion distribution?
describes the number of successes in blocks in time in space.
what is a clumped distribution?
when successes occur more closely together.
what is dispersed distribution?
when successes are more spread out.
what is the formula for possion distribution?
( e to the -u times U to the X) over X!
what is the main property of poission distribution?
variance = mean
