The Point System

[pnunemacher-migration]

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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