# QUIZ 5-4 - α-α--χ ⋅ χ ⋅ 2 2 1 2 2 2 2 s s 1 , 1 n n...

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

STAT 400 Spring 2011 Version D Name ANSWERS . Quiz 5 (10 points) Be sure to show all your work; your partial credit might depend on it. No credit will be given without supporting work. 1. A sample of 10 adult male giraffes had an average height of 15.7 feet, with a sample standard deviation of 0.9 feet. Assume that the population of adult male giraffe heights is normally distributed. a) (3) Construct a 90% confidence interval for the overall average height of adult male giraffes. σ is unknown The confidence interval: X t s ± α 2 n . n - 1 = 10 - 1 = 9 degrees of freedom α = 0.10 t 0.05 ( 9 ) = 1.833 10 9 . 0 833 . 1 7 . 15 ± 15.7 ± 0.52 ( 15.18 ; 16.22 ) b) (4) Construct a 95% confidence interval for the overall standard deviation of the heights of adult male giraffes. The confidence interval : ( ) ( )

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.

Unformatted text preview: α-α--χ ⋅ χ ⋅ 2 2 1 2 2 2 2 s s 1 , 1 n n . 95% confidence level α = 0.05 α 2 = 0.025 . n-1 = 10 -1 = 9 degrees of freedom. 2 025 2 2 . χ χ = α = 19.02. 2 975 2 2 1 . χ χ = α-= 2.700. ( ) ( ) --⋅ ⋅ 700 . 2 9 . 1 10 , 02 . 19 9 . 1 10 2 2 ( 0.619 , 1.643 ) 1. (continued) c) (3) What is the minimum sample size required if we wish to estimate the overall average height of adult male giraffes to within 0.2 feet with 90% confidence, if the overall standard deviation of the heights is 0.8 feet? ε = 0.2 σ = 0.8 α = 0.10 z 0.05 = 1.645 2 2 2 2 . 8 . 645 . 1 α ε σ z = = ⋅ ⋅ n = 43.2964. Round up. n = 44 ....
View Full Document

## This note was uploaded on 11/28/2011 for the course STAT 400 taught by Professor Kim during the Spring '08 term at University of Illinois, Urbana Champaign.

### Page1 / 2

QUIZ 5-4 - α-α--χ ⋅ χ ⋅ 2 2 1 2 2 2 2 s s 1 , 1 n n...

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

View Full Document
Ask a homework question - tutors are online