AP Stats Unit 6-Confidence Interval Procedures

Estimating the proportion of of successes in a single population

Independence:

Data collected using a random Sample

Sample Size n is ≥10% of N

Approximately Normal:

Large counts n(p̂ )≥ 10 and n(1-p̂ )≥10

CI= point estimate ± margin of error

Value of random variable

Ex: p̂ or x̄

critical value(standard error of statistic)

Estimating the difference in proportions

When either:

2 random samples have been selected

subjects are randomly assigned to 2 random groups

Independence:

Data collected using TWO random Samples

Sample Size n is ≥10% of N for BOTH samples

Approximately Normal:

Large counts n(p̂ )≥ 10 and n(1-p̂ )≥10 for BOTH samples

(p1-p2)± z*(standard error of statistic)

Estimating the difference in means

Estimating the mean in a single population

Independence:

Data collected using a random sample

Sample Size n is ≥10% of N

Normal Distribution:

n is greater than or equal to 30

If n < 30 data MUST be free from strong skewness or outliers

Inverse t distribution

area: 1 - C% as a decimal…divide that value by 2

df: n-1

Inverse norm distribution

area (Central): C% as a decimal

mean: 0

SD: 1

sample comes from