The Point System
How accurate is the point system?
A recent post by Kerry about the low point value received for a coin got me wondering. After all my last post was about developing a price/point ratio for purchases.
I decided that a little basic statistics work was required. Using the data available (admittedly as small and limited sample of MS66 quarters from 1949-1960) the results were encouraging.
Sample Size: 38
Mean: 254
Median: 234
Standard Deviation: 78 (rounded to a whole number)
95% Confidence: .79
Outliers at 1 S.D.: 4 on low side, 5 on high side
Outliers at 1.5 S.D.: none on low side, 3 on high side
Outliers at 2.0 S.D.: none on low side, 1 on high side
The remaining outlier was at nearly 4 S.D.
Researching the population/census figures explains the outliers.
All in all, I'm pretty confident that for my sample the points assigned are a reflection of reality. Individual points for a specific coin may seem low (and I have my own opinions on a few) but overall in a series they are pretty good.
Happy collecting,
Phil
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