Riddles of Reckoning: A Statistics Puzzle

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Across
  1. 2. In gatherings oft I make myself known, For I am the number most frequently shown.
  2. 4. In four I part the ordered host, From poorest to richest, each takes their post. Find me to see where the middles abide, The quarters of data I evenly divide.
  3. 7. I measure how far the flock doth stray, From shepherd’s mean along the way. The greater I grow, the wilder the band; The smaller I be, the tighter they stand.
  4. 8. Oft I repeat in measured song, How many times I come along.
Down
  1. 1. I bind together many numbers as one, Dividing their sum ‘til the reckoning is done.
  2. 3. I stray from the crowd, peculiar, untrue, an odd one apart, yet counted still too.
  3. 5. Ordered in line from least unto most, I dwell in the middle, neither boast nor coast.
  4. 6. I am the square of scatter’s might, A measure of spread in numbers’ flight. Before the root, I dwell unseen, Yet with me, deviation is gleaned.