AP Statistics Unit 8

point estimator

a statistic that provides an estimate of a population parameter

confidence interval

an interval of plausible values for a parameter based on sample data (most common is 95%)

confidence level C

the overall success rate of method used to calculate confidence interval - “we are C% confident that interval _ captures % of parameter.”

margin of error

how far (at most) estimate is expected to vary from point estimator in C% confidence interval

decreasing margin of error…

confidence level decreases; sample size increases

critical value

a multiplier that makes interval wide enough to have the stated capture rate

3 conditions for validity of confidence interval p…

1. random sample
2. large counts: np^ ≥ 100 & n(1-p^) ≥ 100


1. 10%: n < 0.10N

standard error

estimate of the standard deviation of a statistic via data

confidence interval

point estimate ± margin of error OR statistic ± critical standard error

confidence interval for p1-p2

statistic ± (critical value)(standard deviation of statistic)

randomized comparative experiment

subjects are randomly assigned to different treatment groups, response variable is tested.