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

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

View Full Document Right Arrow Icon
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 : ( ) ( )
Background image of page 1

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

View Full DocumentRight Arrow Icon
Background image of page 2
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 Right Arrow Icon
Ask a homework question - tutors are online