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.  =   ~
  ~ 
where,  = sample mean =
 = sample mean =  = 441
 = 441
             s = sample standard deviation =  = 14.34
  = 14.34
             n = sample size = 16
              = population mean
 = population mean 
<em>Here for constructing a 95% confidence interval we have used One-sample t-test statistics as we don't know about population standard deviation.</em>
<em />
<u>So, 95% confidence interval for the population mean, </u> <u> is ;</u>
<u> is ;</u>
P(-2.131 <  < 2.131) = 0.95  {As the critical value of t at 15 degrees of
 < 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 <  < 2.131) = 0.95
 < 2.131) = 0.95
P(  <
 <  <
 <  ) = 0.95
 ) = 0.95
P(  <
 <  <
 <  ) = 0.95
 ) = 0.95
<u>95% confidence interval for</u>  = [
 = [  ,
 ,  ]
 ]
                                       = [  ,
 ,  ]
 ]
                                       = [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.