Sociology dating curve
The gramophone sat in your parlor and certainly couldn't be carried along with you and your earbobs. When 78 rpm records first appeared on the market, they were very rare.
When they became popularly available, you could find them everywhere; but then the technology changed and they became rare again. Archaeologists investigate trash, not shop window displays, so we measure things when they are discarded; in this example, we're going to use junkyards.
Absolute dating techniques were not available to him (radiocarbon dating wasn't invented until the 1940s); and since they were separately excavated graves, stratigraphy was no use either.
Petrie knew that styles of pottery seemed to come and go over time--in his case, he noted that some ceramic urns from the graves had handles and others had just stylized ridges in the same location on similarly shaped urns.
It isn't possible to investigate all of a junkyard, so we'll pick a representative sample of the deposit.
We take our samples back to the laboratory, and count the kinds of artifacts in them, and discover that each of the junkyards have broken pieces of musical recording methods in them--old broken records, pieces of stereo equipment, 8-track cassette tapes.
Larger percentages of artifact types are illustrated with longer bar snippets and smaller percentages with shorter bar snippets.
A good source of information about how to make charts in Excel is Ted French's Excel Chart Tutorial (for several different versions of Excel).
Of all the music recording artifacts in our sample from Junkyard E, 10% are related to 45 rpm technology; 20% to 8-tracks; 60% are related to cassette tapes and 10% are CD-Rom parts.The figure on this page is a Microsoft Excel (TM) table showing the results of our frequency count.Our next step is to create a bar graph of the percentages of the objects in our junkyard samples.Using seriation at our hypothetical junkyard sites, we will try to establish the chronology--the order in which the junkyards were used and closed.To start out, we will take a sample of the deposits in each of junkyards.