Eric Bohlman <[EMAIL PROTECTED]> wrote in message news:<[EMAIL PROTECTED]>... > "R. Martin" <[EMAIL PROTECTED]> wrote in news:[EMAIL PROTECTED]: > > > John E wrote: > >> > >> Where can I information specifically on trends and patterns deduced from > >> histograms? I have to write a report based on this form of data and I'm > >> unsure of exactly what to do. > > > > To get an answer I think you need to define what you mean by "trends > > and patterns". Histograms collapse all the temporal information and > > so trends can not be discerned from a histogram. A series of > > histograms plotted from data obtained at different times will show > > trends in how the histogram changes, if that is what you are referring > > to. > > W. Edwards Deming used to give an example of a misleading histogram in his > lectures. It involved measurements of the elongation of a spring that was > part of a camera. The histogram showed a very nice near-normal > distribution centered exactly at the nominal specification for the spring's > elongation. But a plot of elongations in order of production showed a > downward trend over time; the process that was producing the springs was > deteriorating and was on the verge of producing mostly out-of-spec springs. > How close your spring was to the nominal spec depended on when you bought > it, but you wouldn't know it from the histogram.
>From what I've read, he had many illustrative and educational things in his lectures. I wish I would have had a chance to attend some. So, how did that come about. Were the early springs close to out of spec on the other side? (I might be able to figure this out by myself, but I've just finished an operational shift and my mind is fried.) Regards, Russell . . ================================================================= Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at: . http://jse.stat.ncsu.edu/ . =================================================================
