how to
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take a random sample
1- Create a list of every unit in the population of interest, and give each unit a number between one and the total population size 2- Decide on the number of units to be sampled (call this number n) 3- Using a random-number generator, generate n random integers between one and the total number of units in the population 4- sample the units whose numbers match those produced by the random-number generator
calculate goodness of fit (x^2)
x^2= sum of all classes [(observed-expected)^2/expected]
How to calculate degrees of freedom for goodness of fit test
df= (number of categories) - (number of parameters estimated from the data) -1
How do you find the P-value for goodness of fit?
• find the 5% critical value • look at df for alpha of 0.05 on x^2 distribution table • table will tell you critical value for x^2 for that many degrees of freedom
Poisson distribution
Pr[x]= e^-u u^X/ X! X= the number of events u= the mean number of events per unit
degrees of freedom in a contingency analysis
df= (#column-1)(#rows-1)