Quote:
Originally Posted by MetroMPG
More inflation vs. rolling resistance data for the pile.
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Thank you for your diligence and care. Since data analysis (especially small-sample analysis) comprised the second half of my professional career (from which I am now retired) I entertained myself tonight by exercising some remaining brain cells with my own spreadsheet (OpenOffice Calc) analysis of these data, verified with software by Richard Lowry at Vassar:
Spearman rank correlation* (SRC) between 70psi and 60psi of feet travelled is -0.488, a weak (insignificant) decrease of feet above 60psi.
Including the 50psi data gives a SRC of +0.133, a very weak (insignificant) increase of feet above 50psi.
Including the 40psi data gives a SRC of +0.644, a strong (significant at 0.012 level) increase of feet above 40psi.
It's therefore clear that increasing pressure above 40psi results in an increase in feet, and that increasing pressure above 50psi does not.
*chosen because the data are non-linearly related.