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FORVM`s Classical Numismatics Discussion Board  |  Numism  |  Reading For the Advanced Collector  |  Topic: What is a Raven Index? 0 Members and 1 Guest are viewing this topic. « previous next »
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Tracy Aiello
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« on: July 01, 2019, 06:20:38 pm »

Hello,

Perhaps this post doesn’t belong here but I couldn’t find another place on this discussion board where I thought that it fit.

I am currently reading Catharine Lorber’s “A Hoard of Facing Head Larissa Drachms” in SNR 79 (2000) and have come across the term “Raven index”. Oddly enough when I search the web for that term nothing comes up. I also don’t find anything in NumisWiki or on this discussion board. So,...is someone able to explain to me what a “Raven index” is?

Thank you very much.

Tracy
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BiancasDad
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« Reply #1 on: July 01, 2019, 07:41:19 pm »

This may be way off base but this article mentions someone by the name of Raven with a mathematical discussion related to finding certain obverse dies in a series of coins.

https://www.academia.edu/8889545/The_Royal_Seleucid_Mint_of_Seleucia_on_the_Calycadnus

From page 96:

"P. Raven has noted, and W. McGovern has demonstrated mathematically (64), that the likelihood of finding at least one or more additional full-life obverse dies within a short series (less than fifteen coins) is about equal if the ratio of known coins to known obverse dies (the index figure) is around 2 (65)."

Sorry if this is way off base but I love a good "who dunnit" mystery.
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n.igma
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« Reply #2 on: July 01, 2019, 09:06:53 pm »


"P. Raven has noted, and W. McGovern has demonstrated mathematically (64), that the likelihood of finding at least one or more additional full-life obverse dies within a short series (less than fifteen coins) is about equal if the ratio of known coins to known obverse dies (the index figure) is around 2 (65)."


This is the origin of the Raven Index. Mathematically it is equal to (the number of coins in a sample)/(the number of dies in a sample) = n/d. It is more correctly termed the Characteristic Index being in statistical terms a crude measure of the the statistical significance of the sample. The higher the number the more representative is the sample of the total population.

Statistical analysis has moved a long way forward from Raven's day (over 50 years ago !!!), although most numismatists have yet to catch up with the progress, which is why some still refer to the Raven Index. Far better is the measure of Statistical Coverage (Cest) provided by Warren Esty whose work can be found here: https://montana.academia.edu/WarrenEsty

In particular two of his papers provide definitive equations for handling statistical analysis of die studies:
1) The Geometric Model for Estimating the Number of Dies  https://www.academia.edu/573364/The_Geometric_Model_for_Estimating_the_Number_of_Dies
2) How to estimate the original number of dies and the coverage of a sample https://www.academia.edu/1293727/How_to_estimate_the_original_number_of_dies_and_the_coverage_of_a_sample

Forget about Raven's antiquated methodology and go with Esty's geometrical model.  You'll be in company of the numismatic greats: e.g. F. de Callatay:
1) Quantifying monetary production in Greco-Roman times: a general frame https://www.academia.edu/473995/Quantifying_monetary_production_in_Greco-Roman_times_a_general_frame
2) The contents page of the total volume on this topic: https://www.academia.edu/2065356/F._de_Callata%C3%BF_ed._Quantifying_monetary_supplies_in_Greco-Roman_times_Pragmateiai_19_Bari_Edipuglia_2011_330_p
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Tracy Aiello
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« Reply #3 on: July 02, 2019, 06:38:37 am »

BiancasDad,

Since the mention of the Raven index was in the context of discussing dies you are not off base. Thank you for responding.

Tracy
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Tracy Aiello
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« Reply #4 on: July 02, 2019, 06:39:35 am »

 n.igma,

Thank you for the latest and greatest information. I won't understand Esty's article (I'm not very mathematically inclined) but I will check it out.

Tracy
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