"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. . . ================================================================= Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at: . http://jse.stat.ncsu.edu/ . =================================================================
