Demetrios I

Founded 17-Feb-2004
Last update 25-Mar-2004

Antioch Mint - Undated Issues References


Antioch Mint – Undated Issues

1. Examined type

Denomination: AR Tetradrachm
Period: 162/1 - 155/4 BC
Obverse: Diademed head of Demetrios right; laurel wreath border
Reverse: ‘ΒΑΣΙΛΕΩΣ’ on right, ‘ΔΗΜΗΤΡΙΟΥ’ on left; Tyche, nude to waist, holding short sceptre with right hand and cornucopiae with left arm, seated left on throne with winged lion’s foot support

2. Acceptable weight range

Lower exclusion limit: 15.75 grams
Upper exclusion limit: 17.25 grams

Each coin is a priori excluded from the data sample if its weight is lesser than the lower exclusion limit or greater than the upper exclusion limit.

3. Data

The data sample was kindly provided by Arthur Houghton who accumulated it in the course of a die study of the precious metal coinage of the mint of Antioch under Demetrios I and later rulers (a part of the material regarding undated Antioch tetradrachms of Demetrios I was accumulated by Richard Miller). The data refers only to the Antioch mint and to no other.

4. Descriptive statistics

No. of observations: 332  
Mean: 16.56 (95% confidence interval: 16.54 ≤ mean ≤ 16.58)
Standard deviation: 0.22  
Interquartile range: 0.27  
Skewness: -0.97  
Kurtosis: 3.92  
Minimum: 15.76  
25th percentile: 16.45 (95.1% confidence interval: 16.40 ≤ 25th percentile ≤ 16.49)
Median: 16.60 (94.5% confidence interval: 16.57 ≤ median ≤ 16.63)
75th percentile: 16.72 (95.1% confidence interval: 16.69 ≤ 75th percentile ≤ 16.75)
Maximum: 16.98  

Notes: The unbiased estimation of the variance was used for the computation of the standard deviation (i.e. the number of observations minus one was used as a divisor). The sample skewness was computed without sample corrections (i.e. the skewness was computed as the square root of the number of observations times the sum of the third powers of deviations from the mean divided by the 3/2 power of the sum of the squares of deviations from the mean). Similarly, the sample kurtosis was computed as the number of observations times the sum of the fourth powers of deviations from the mean divided by the second power of the sum of the squares of deviations from the mean.

The confidence interval for mean was computed by using the Student t-distribution. The confidence intervals for median and percentiles were computed nonparametrically by using the binomial distribution (see, e.g., Conover, Practical Nonparametric Statistics, pp. 143 - 148).

5. Estimation of proportion of coins with weights within the observed range

At the 95% level of confidence, at least 98.6% of issued coins of the examined type have a weight between the smallest observation and the largest observation, i.e. between 15.76 g and 16.98 g, and at least 97.7% of issued coins of the examined type have a weight between the second smallest observation and the second largest observation, i.e. between 15.79 g and 16.97 g.

Note: These estimations are computed as tolerance limits based on the binomial distribution. See, e.g., Conover, Practical Nonparametric Statistics, pp. 150 - 155.

6. Histogram and probability density function

Histogram of the sample is presented in Figure 1. Kernel estimations of the probability density function are shown in Figure 2 (two kernel estimations were used: Epanechnikov kernel with a bandwidth of 0.054 and Gaussian kernel with a bandwidth of 0.056). The dotted curve in Figure 2 is a probability density function of a normal distribution estimated by the maximum likelihood method.

Note: The bandwidth of the Gaussian kernel was computed as hGauss = 0.9 × min(σ, SIQR) × n-1/5, where σ is the standard deviation, SIQR is the standardised interquartile range (i.e. the interquartile range of the data sample divided by the interquartile range of the standard normal density) and n is the number of observations; see Silverman, Density Estimation for Statistics and Data Analysis, p. 48, formula (3.31). The bandwidth of the Epanechnikov kernel was chosen subjectively in the range from 0.75×hGauss to 1.25×hGauss.

Fig. 1: Histogram

Fig. 1: Histogram

Fig. 2: Probability density estimations

Fig. 2: Probability density estimations

7. Test of normality

The Lilliefors test of normality was used. The test statistic of 0.094 is greater than the cutoff value of 0.049 for a 95% level test. Thus we reject the hypothesis of normality at the 95% level of significance. Normal probability plot of the sample is presented in Figure 3.

Fig. 3: Normal probability plot

Fig. 3: Normal probability plot

 


References:

Conover, W. J.:Practical Nonparametric Statistics, Third Edition. John Wiley & Sons, Inc., New York - Chichester - Weinheim - Brisbane - Singapore - Toronto, 1999.
Silverman, B.W.:Density Estimation for Statistics and Data Analysis. Chapman and Hall, London - New York - Tokyo - Melbourne - Madras, 1993 (reprint of the first edition published in 1986).