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Which formula to use:

posted Feb 19, 2010, 7:59 AM by Prof Kiernan

parameter Conditions/given Confidence Interval
test statistic Key words
Proportion nP > 5 & nQ < 5

given:
population proportion (P)

sample proportion
(p = x/n)

q=1-p & Q=1-P
 

Proportion

Percent

You are not given a standard deviation
Mean population data known
OR
n > 30


GIVEN:
σ (population standard deviation)
population mean (μ)         _
sample mean: X
sample size = n
 
 
You know what the population standard deviation is.
Mean population data NOT known
and n < 30

GIVEN:
s (sample standard deviation)
population mean (μ)         _
sample mean: X
sample size = n
 
 
Given sample info
Standard deviation
OR variance(σ²)
Population normally distributed
GIVEN:
σ (population standard deviation)
sample size = n
s (sample standard deviation) 
 

You're working with a hypothesis
about the standard
deviation of a sample
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