Chapter 8 AP Statistics

STUDY
PLAY
point estimator
a statistic that provides an estimate of a population parameter
point estimate
the value of a statistic from a sample
C% confidence interval
gives an interval of plausible values for a parameter
point estimate +/- margin of error
margin of error
shows how close we believe our guess is, based on the variability of the estimate in repeated SRSs of the same size
critical value x standard deviation of statistic
confidence level C
In C% of all possible samples, the method would yield an interval that captures the true parameter value.
interpretation of confidence interval
We are C% confidence that the interval from ___ to ___ captures the true population [parameter in context].
conditions for estimating population parameters
SRS, Independent, Normal
standard error
when the standard deviation of the statistic is estimated from data
The four step process
State, Plan, Do, Conclude
degrees of freedom
for a t-distribution, this is required in order to find the critical value
n-1
z*
critical value for proportions
t*
critical value for means, population standard deviation unknown
Normal condition for means
CLT, n>= 30
if n<30, then no skewness or outliers if graphed
Normal condition for proportions
np>10, n(1-p)>10
Independent condition
sample size is less than 10% of the population
random condition (SRS)
the sample must come from a well-designed random sample or randomized experiment
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