# Understanding Variation Problems

Understanding Variation Problems
1)   The data file for this problem contains 82 consecutive values for the amount of deviation (in .000025 inch units) from a specified target value that an industrial machining process at a large manufacturer produced under specified operating conditions.   Thus in the data 0 means that the value was right on target and -3 means that the part produced measured .000075 inches below the target value.
a)   Use Minitab to produce a time series plot of this data.
b)   Describe the plot.   Is this process characterized by only common causes or are there any special causes?   Is there anything unusual about this data?
2)   The data file for this problem contains the average hourly wage (multiplied by 100) for U. S. workers in the manufacturing industries by month over the period from July 1981 to June 1987.
a)   Use Minitab to produce a time series plot of this data.   Describe the plot, what are the most important features of the plot.
b)   Use Minitab to construct the month to month differences of the average hourly wage data.   (Instructions on how to do this are given below.)   Plot the month to month differences of this data.   Describe the plot, what are the most important features of this plot?
To form the month to month differences go to the “Stat” menu, select the item “Time Series” from the submenu, and select the item “Differences” from the resulting submenu.   In the subsequent window type the column that has the manufacturing wages into the box labeled “Series” and type the column you wish to store the month to month differences in the box labeled “Store differences in”.   Click OK.
3)   The data for this problem are monthly sales of a low cost replacement oil filter made by John Deere.   The data covers a 48 month period beginning in July of one year and ending in June four years later.
a)   Use Minitab to produce a time series plot of this data.   Describe the plot.   What are the most important features of the plot.
b)   Use...