Respuesta :
Answer:
(a) A 95% confidence interval for the population mean is [433.36 , 448.64].
(b) A 95% upper confidence bound for the population mean is 448.64.
Step-by-step explanation:
We are given that article contained the following observations on degrees of polymerization for paper specimens for which viscosity times concentration fell in a certain middle range:
420, 425, 427, 427, 432, 433, 434, 437, 439, 446, 447, 448, 453, 454, 465, 469.
Firstly, the pivotal quantity for finding the confidence interval for the population mean is given by;
P.Q. = [tex]\frac{\bar X-\mu}{\frac{s}{\sqrt{n} } }[/tex] ~ [tex]t_n_-_1[/tex]
where, [tex]\bar X[/tex] = sample mean = [tex]\frac{\sum X}{n}[/tex] = 441
s = sample standard deviation = [tex]\sqrt{\frac{\sum (X-\bar X)^{2} }{n-1} }[/tex] = 14.34
n = sample size = 16
[tex]\mu[/tex] = population mean
Here for constructing a 95% confidence interval we have used One-sample t-test statistics as we don't know about population standard deviation.
So, 95% confidence interval for the population mean, [tex]\mu[/tex] is ;
P(-2.131 < [tex]t_1_5[/tex] < 2.131) = 0.95 {As the critical value of t at 15 degrees of
freedom are -2.131 & 2.131 with P = 2.5%}
P(-2.131 < [tex]\frac{\bar X-\mu}{\frac{s}{\sqrt{n} } }[/tex] < 2.131) = 0.95
P( [tex]-2.131 \times {\frac{s}{\sqrt{n} } }[/tex] < [tex]{\bar X-\mu}[/tex] < [tex]2.131 \times {\frac{s}{\sqrt{n} } }[/tex] ) = 0.95
P( [tex]\bar X-2.131 \times {\frac{s}{\sqrt{n} } }[/tex] < [tex]\mu[/tex] < [tex]\bar X+2.131 \times {\frac{s}{\sqrt{n} } }[/tex] ) = 0.95
95% confidence interval for [tex]\mu[/tex] = [ [tex]\bar X -2.131 \times {\frac{s}{\sqrt{n} } }[/tex] , [tex]\bar X +2.131 \times {\frac{s}{\sqrt{n} } }[/tex] ]
= [ [tex]441-2.131 \times {\frac{14.34}{\sqrt{16} } }[/tex] , [tex]441+2.131 \times {\frac{14.34}{\sqrt{16} } }[/tex] ]
= [433.36 , 448.64]
(a) Therefore, a 95% confidence interval for the population mean is [433.36 , 448.64].
The interpretation of the above interval is that we are 95% confident that the population mean will lie between 433.36 and 448.64.
(b) A 95% upper confidence bound for the population mean is 448.64 which means that we are 95% confident that the population mean will not be more than 448.64.
