typewritten solution

2points Q An electrical rm manufactures light bulbs that have a length of life that is appropriately normally distributed with a standard deviation of 40 hours. If a sample of 40 bulbs has an average life of 780 hours, nd a 95% condence interval for the population mean of all bulbs produced by this rm. 767.6039su37923961 76887785115791 .1222 Q 76119495115798.8051 769.109OSuS790.8910 4points 5' A machine produces metal pieces that are cylindrical in shape. A sample of pieces is taken, and the diameters are found to be 1.01, 0.97, 1.03, 1.04, 0.99, 0.98, 0.99, 1.01, 1.03, 0.99, 1.00, 1.06, 1.03 and 0.96. Find a 99% condence interval for the mean diameter of pieces from this machine, assuming an approximately normal distribution. (edited - correction for the sd) 0.98335us10295 0.9939sus 1.0234 0.9967sus 1.0233 0.9907sus 1.0235 2points A random sample of size n1=25, taken from a normal population with a standard deviation 01:5, has a mean )'(1=80. A second random sample of size n2=36, taken from a different normal population with a standard deviation 02=3, has a mean 22:75. Find a 99% confidence interval for p1-p2. 3.16085H1-\"256.8392