= M. M. Slining
{c}
\b[<M. M. Slining>] is a coauthor of the 2010 study of human <nail (anatomy)> growth with <S. Yaemsiri>, <N. Hou> and <K. He>. Participants recorded displacement of nail marks over follow-up, allowing <growth rate> to be computed from distance and time.<Growth rate of human fingernails and toenails in healthy American young adults by S. Yaemsiri and others>[Byline; Abstract, Methods]{ref} The record verifies this scientific collaboration while leaving the initials unexpanded.
A methodological lesson concerns averaging when observation intervals differ. Consider an original two-observation example: one mark advances 3 millimetres in one month, another 8 millimetres in two months. Their rates are 3 and 4 millimetres per month. Equal weighting of the two rates gives
$$
\overline v=\frac{3+4}{2}=3.5\,\mathrm{mm\,month^{-1}},
$$
whereas total displacement divided by total observed time gives
$$
v_{\mathrm{pooled}}=\frac{3+8}{1+2}=\frac{11}{3}\,\mathrm{mm\,month^{-1}}.
$$
The pooled calculation weights the longer interval more heavily. Neither arithmetic error nor biological contradiction explains their difference: they answer differently weighted questions.
For a <longitudinal study>, the desired estimand determines the summary. An equal-person average, an average over measured nails and an elapsed-time-weighted average can differ. Measurement uncertainty and dependence among nails also affect precision. The original example illustrates interpretation of the published method; it does not attribute a particular statistical choice or individual task to Slining.
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