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statistic

It can be Excel or a picture of a paper with the solutions.

Please she knows im not good with excel, so make it as simple as possible. 

Directions: you must submit your initial answers to the homework and I will check whether you are on the right path.  All of the problems require calculations from Ch. 10.1 and 10.4.  They are not simple read and response problems.  You must have a calculation for your interpretation. 

I recommend you use Excel   to complete this exercise and take a look at the file posted on Moodle titled

             “Ch 9 and 10 in Excel

1. The operations manager at a lightbulb factory wants to determine whether there is any difference in the mean life expectancy of bulbs manufactured on two different machines.  The population standard deviation of machines I is 110 hours and of machine II is 125 hours. A random sample of 25 light bulbs from machine I indicates a mean of 375 hours and a similar sample of 25 lightbulbs indicates a sample of 362 hours for machine II

a. Using the .05 level of significance is there any evidence of a difference in the mean life of light bulbs produced by the two-types of machines.

2. A bank with a branch located in a commercial district of a city has developed an improved process for serving customers during the noon to 1 pm lunch period.  The waiting time(operationally defined as the time elapsed from when the customer enters the line until he or she reaches the teller window) of all customers during this hour is recorded over a period of one week. A random sample of 15 customers Bank1 is selected and the results (in minutes) are as follows:

4.21   5.55   3.02   5.13    4.77   2.34   3.54    3.20    4.50    6.10   0.38   5.12   6.46    6.19    3.79

Suppose that another branch located in a residential area is also concerned with the noon to 1 pm lunch period. A random sample of 15 customers Bank2  and the results are as follows

9.66   5.90   8.02   5.79   8.73   3.82   8.01   8.35   10.49   6.68   5.64   4.08   6.17   9.91   5.47

a. Assume that the population variances from both banks are equal, is there evidence of a difference in the mean waiting times between the two branches (Use a=0.05)

b. What other assumption is necessary in (a)

c. Assuming that the population variances from both branches are equal, construct  and interpret 95% confidence interval estimate of the difference between the population means in the two branches