Torsion during hip external rotation $($ER$)$ and extension may be responsible for certain kinds of injuries in golfers and other athletes. The article "Hip Rotational Velocities During the Full Golf Swing"$$ reported on a study in which peak ER velocity and peak IR $($internal rotation$)$ velocity $($both in deg$$sec$1)$ were determined for a sample of $15$ female collegiate golfers during their swings. The following data was supplied by the article's authors.

Golfer ER IR diff z perc

$1130\mathrm{.}698\mathrm{.}931\mathrm{.}71\mathrm{.}28$

$2125\mathrm{.}1115\mathrm{.}99\mathrm{.}20\mathrm{.}97$

$351\mathrm{.}7161\mathrm{.}6109\mathrm{.}90\mathrm{.}34$

$4179\mathrm{.}7196\mathrm{.}917\mathrm{.}20\mathrm{.}73$

$5130\mathrm{.}5170\mathrm{.}740\mathrm{.}20\mathrm{.}34$

$6101\mathrm{.}0274\mathrm{.}9173\mathrm{.}90\mathrm{.}97$

$724\mathrm{.}4275\mathrm{.}0250\mathrm{.}61\mathrm{.}83$

$8231\mathrm{.}1275\mathrm{.}744\mathrm{.}60\mathrm{.}17$

$9186\mathrm{.}8214\mathrm{.}627\mathrm{.}80\mathrm{.}52$

$1058\mathrm{.}5117\mathrm{.}859\mathrm{.}30\mathrm{.}00$

$11219\mathrm{.}3326\mathrm{.}7107\mathrm{.}40\mathrm{.}17$

$12113\mathrm{.}1272\mathrm{.}9159\mathrm{.}80\mathrm{.}73$

$13244\mathrm{.}3429\mathrm{.}1184\mathrm{.}81\mathrm{.}28$

$14184\mathrm{.}4140\mathrm{.}643\mathrm{.}81\mathrm{.}83$

$15199\mathrm{.}2345\mathrm{.}6146\mathrm{.}40\mathrm{.}52$