lab4 - Confidence Intervals Allows a statement of...

This preview shows pages 1–2. Sign up to view the full content.

1 Confidence Intervals • Allows a statement of confidence about the estimate of the population parameter. • If you were to take a large number of samples, and calculate the CI for each sample, then about 95% (or 99%, if that’s the CI) of them would contain the parameter value. x x x x x x x x σ + µ σ σ + µ σ 58 . 2 58 . 2 : CI % 99 96 . 1 96 . 1 : CI % 95 • The mean score for high school students on an achievement exam is 475 with . You randomly sample 10 students from CPS and obtain a mean of 480 • Given , find the 95% confidence interval for the mean. – First, calculate the standard error, 10 , 10 480, X = = σ = n 10 3.162 10 x n σ == = () 95% CI: 1.96 1.96 480 1.96(3.162) 480 1.96(3.162) 480 6.198 480 6.198 473.802 486.198 .95 xx C µσ µ ≤≤ + −≤ + + = 99% CI: 2.58 2.58 480 2.58(3.162) 480 2.58(3.162) 480 8.158 480 8.158 471.842 488.158 .95 C + + + = 10 = • Calculate the 95% CI with a sample of 100, assuming the same sample mean. Online demonstration - http://www.ruf.rice.edu/~lane/stat_sim/conf_interval/ 1 100 10 : error, standard the affects This x = = σ = σ σ n x 95% CI: 1.96 1.96 480 1.96(1) 480 1.96(1) 478.04 481.196 .95 C + + = Types of errors Good

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 07/17/2008 for the course PHYS 321 taught by Professor Zandt during the Spring '05 term at Ohio State.

Page1 / 3

lab4 - Confidence Intervals Allows a statement of...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online