FROM: R.J. Kurland, Problem Specialist     ÂJK

SUBJECT: Recall Problems

DATE: February 25^th, 1999
 

        The problem with your right production line is due to increased variability in package weights, according to our analysis. The "range" (difference between lowest and highest values) for the right line shows extreme fluctuations (Attachment, Figure A) in the 15 weeks (weeks 11 to 25) following the initial 10 week training period. The corresponding range chart for the left line (Attachment, Figure A) does not show this sudden jump in variability after the 10 week training period.

        Since the variability has increased, the number of low weight packages will also be greater, as shown in Attachment, Figure B; the result is a greater number of returned packages by your customers. Notice that in this plot of low weights for the right line there are many minimum weights below the cutoff value, 11.5 ounces, after the 15^th week, when production speed is up. The left line does not show any minimum weights below the cutoff.

        We do not know why there should be a greater variability in weights for your right line during a full production schedule. You may need to retrain the workers on this line or to check the rough weight machines. (Exchanging left and right line workers might show whether the work force or the machines are responsible for your problems.) As you pointed out to us, the mean values for both lines are about the same, so differences in average weights is not a problem.

    Please call on our services again when you need to know about numbers and all they can do for you.