STAT 400 Lecture AL1 Examples for 7 1 Part 3 Spring 2015 Dalpiaz EXCEL CHIINV v 2 v for 2 distribution with v degrees gives of freedom CHIDIST y v gives the upper tail probability for 2 distribution with v degrees of freedom P Y y Recall If X 1 X 2 X n are i i d N 2 Then n 1 S 2 2 X i X 2 2 is 2 n 1 A 1 100 confidence interval for the population variance 2 where the population is assumed normal 2 n 1 s 2 2 n 1 s 2 1 2 2 n 1 degrees of freedom A 1 100 confidence interval for the population standard deviation where the population is assumed normal n 1 s 2 2 2 n 1 s 2 1 2 2 OR s n 1 s 2 2 n 1 2 1 2 n 1 degrees of freedom 1 A machine makes inch ball bearings In a random sample of 41 bearings the sample standard deviation of the diameters of the bearings was 0 02 inch Assume that the diameters of the bearings are approximately normally distributed Construct a 90 confidence interval for the standard deviation of the diameters of the bearings 2 The following random sample was obtained from N 2 distribution 16 Recall 12 x 15 18 13 s 2 16 21 15 8 17 s 4 a Construct a 95 confidence interval for the overall standard deviation b Construct a 95 confidence lower bound for the overall standard deviation c Construct a 95 confidence upper bound for the overall standard deviation
View Full Document
Unlocking...