Step 1. The twenty months of the hand example (July 1926 to February 1928):
  20 months    n=  20  mean +1.85  median +2.29  sd 3.16  IQR 3.37  min -4.04  max +7.56  skew -0.03  positive 75.0%
        Q1 +0.07  Q3 +3.44  range 11.60 points

Step 2. Full series, 1,194 months:
  Full series  n=1194  mean +0.96  median +1.34  sd 5.30  IQR 5.73  min -28.71  max +38.91  skew +0.12  positive 62.9%
        Bowley (quantile) skewness -0.09

Step 3. Table 2.1, descriptive statistics by era:
  1926 to 1969 n= 522  mean +0.94  median +1.30  sd 6.12  IQR 5.79  min -28.71  max +38.91  skew +0.46  positive 63.4%
  1970 to 1999 n= 360  mean +1.17  median +1.33  sd 4.59  IQR 5.97  min -22.59  max +16.62  skew -0.51  positive 61.1%
  2000 to 2025 n= 312  mean +0.77  median +1.35  sd 4.52  IQR 5.38  min -17.12  max +13.60  skew -0.50  positive 64.1%

Step 4. Percentile ladder, full series (book's rule, type 7):
   1st percentile: -13.41 percent
   5th percentile: -7.55 percent
   25th percentile: -1.78 percent
   50th percentile: +1.34 percent
   75th percentile: +3.95 percent
   95th percentile: +7.71 percent
   99th percentile: +12.89 percent

Step 5. Pictures written: ch02_figure_histogram.png, ch02_figure_timeplot.png, ch02_figure_boxplot.png
        Read them as Section 2.5 reads them: the histogram forgets the order and shows the shape (a compact center, tails reaching -28.71 and +38.91, far beyond the curve); the time plot keeps the order and shows the regimes; the boxplot is the quartiles of Section 2.6 made visible.

Part B, R lane solution: Table 2.1 for the second index series
  1926 to 1969 n= 527  mean +0.51  median +1.07  sd 5.26  IQR 4.57  min -26.47  max +50.30  skew +1.02  positive 60.3%
        At the lane's three-decimal precision: mean +0.511, median +1.069, standard deviation 5.264, moment skewness +1.019
  1970 to 1999 n= 360  mean +0.83  median +0.75  sd 3.56  IQR 4.06  min -12.56  max +11.58  skew -0.44  positive 60.8%
        At the lane's three-decimal precision: mean +0.831, median +0.749, standard deviation 3.560, moment skewness -0.436
  2000 to 2025 n= 312  mean +0.57  median +1.21  sd 3.71  IQR 3.94  min -20.39  max +12.02  skew -1.48  positive 64.1%
        At the lane's three-decimal precision: mean +0.575, median +1.212, standard deviation 3.712, moment skewness -1.476

Chapter 2 lab complete.
