3. Production Process Characterization
3.5. Case Studies
3.5.2. Machine Screw Case Study

## Box Plots by Factors

Initial Steps The initial step is to plot box plots of the measured diameter for each of the explanatory variables.
Box Plot by Machine The following is a box plot of the diameter by machine.

Conclusions From Box Plot We can make the following conclusions from this box plot.
1. The location appears to be significantly different for the three machines, with machine 2 having the smallest median diameter and machine 1 having the largest median diameter.

2. Machines 1 and 2 have comparable variability while machine 3 has somewhat larger variability.
Box Plot by Day The following is a box plot of the diameter by day.

Conclusions From Box Plot We can draw the following conclusion from this box plot. Neither the location nor the spread seem to differ significantly by day.
Box Plot by Time of Day The following is a box plot of the time of day.

Conclusion From Box Plot We can draw the following conclusion from this box plot. Neither the location nor the spread seem to differ significantly by time of day.
Box Plot by Sample Number The following is a box plot of the sample number.

Conclusion From Box Plot We can draw the following conclusion from this box plot. Although there are some minor differences in location and spread between the samples, these differences do not show a noticeable pattern and do not seem significant.