Chapter 18: Confidence Intervals for Proportions

Question 1

Point Estimator

Answer 1

A statistic that provides an estimate of a population parameter

Question 2

Point Estimate

Answer 2

The value of the point estimator from a sample

Question 3

C% Confidence Interval

Answer 3

An interval of plausible values for a parameter
CI = point estimate ± margin of error
Interval (A,B):
Point estimate = (A+B)/2
Margin of error = (B-A)/2

Question 4

Margin Of Error

Answer 4

How far we expect the sample statistic to vary from its corresponding population parameter, at most, in about ___% of samples

Question 5

Confidence Interval Script

Answer 5

“We are [C%] confident that the interval from [A to B] captures the true [population parameter in context].”

Question 6

Confidence Level Script

Answer 6

“If we take many, many sample and calculate a confidence interval for each, about [C%] will capture the true [population parameter in context].”

Question 7

1-PropZInt Conditions

Answer 7

1. Random sample
2. n≤10% of pop.
3. np≥10 & n(1-p)≥10

Question 8

Margin Of Error Formula

Answer 8

(critical value)*(standard error of statistic)

Question 9

Standard Error

Answer 9

Estimate of standard deviation

Question 10

Critical Value Of Z Distribution Formula

Answer 10

z* = InvNorm ([1-c]/2, μ=0, σ=1)

Question 11

Confidence Interval Of 1-PropZInt On Calculator

Answer 11

x: # of successes
n: sample size
C-Level: CI% as decimal

Question 12

Sample Size & Confidence Level Relating To Margin Of Error

Answer 12

Increase in sample size = decrease in margin of error (narrower interval)
Increase in confidence level = increase in margin of error (wider interval)