#
# Written by:
# -- 
# John L. Weatherwax                2009-04-21
# 
# email: wax@alum.mit.edu
# 
# Please send comments and especially bug reports to the
# above email address.
#
# Computations used for the problems in this section of the text.
#
#-----

save_plots = F

# Ex 7.4
#
x_bar = 58.3
s = 3
n = 25
t_crit = qnorm( 1 - 0.05/2 )
x_bar + s/sqrt(n) * t_crit * c(-1,+1) 

n = 100 
x_bar + s/sqrt(n) * t_crit * c(-1,+1) 

t_crit = qnorm( 1 - 0.01/2 )
x_bar + s/sqrt(n) * t_crit * c(-1,+1) 

t_crit = qnorm( 1 - 0.18/2 )
x_bar + s/sqrt(n) * t_crit * c(-1,+1) 

t_crit = qnorm( 1 - 0.01/2 )
( 2 * t_crit * s )^2 

# Ex 7.10
#
DF = read.csv( "../../Data/CH07/ex7-10.txt", header=TRUE, quote="'" )
n = length(DF$lifetime..yrs.)

a = qchisq( 0.025, 2*n )
b = qchisq( 1-0.025, 2*n )

c( ( 2*sum(DF$lifetime..yrs.) ) / b, ( 2*sum(DF$lifetime..yrs.) ) / a )