Answer Happy

The specifications for vending machines, established by the
Newton Machine Company, require that the machines dispense
quantities of coffee averaging 12 oz. Below are the quantities of
coffee (in ounces) chosen at random from different machines.
a. Use these sample results to construct a 95% confidence
interval for the mean amount of coffee from all cups served. Does
this confidence interval suggest that the machines are working
properly? *Data come from a normal distribution.
11.5 10.8 9.7 13.0 11.5 11.1 9.0 10.6
13.2 11.1 11.1 12.6 6.8 11.4 10.1 10.8
Give Excel equations as well as all procedure.
b. Use the same data from this exercise to construct an
estimated 95% confidence interval for σ. New specifications are
being considered to control variation in the quantities of coffee
shipped. It is desired that almost all quantities dispensed be
within 0.5 oz of 12 oz, and using the range rule of thumb, this
suggests that the standard deviation should be 0.25 oz. Based on
the confidence interval, is the value of 0.25 oz a feasible value
for the population standard deviation? Does the machine require
modifications to reduce variation?