91影视

Value,$x=948$

Mean,$渭=944$

$z鈭�$ score,$z=0.50$

The formula used:$z=\frac{(x-渭)}{蟽}$

$z鈭�$ scores,

For Judy, $z=鈭�1.45$

For Mary, $z=0.50$

The amount of standard deviations a value deviates from the mean is described by the $z鈭�$score.

The value is below the mean when the $z鈭�$score is negative.

Whereas,

Positive $z鈭�$implies that the value is greater than the mean.

That implies

The higher the $z鈭�$score, the better (or healthier).

A higher $z鈭�$score in the reference population suggests higher bone density.

As a result, Mary鈥檚 bones are healthier for her age.

Calculate the $z鈭�$ score:

$z=\frac{x鈭�渭}{蟽}$

Substitute values,

$0.50=\frac{948鈭�944}{蟽}$

That becomes

$0.50=\frac{4}{蟽}$

That further becomes

$蟽=\frac{4}{0.50}=8$

Because the standard deviation and data values have the same units.

Thus,

The standard deviation is $8g/{cm}^2$

Surprisingly, the standard deviation of the density in Mary鈥檚 case is higher than that of Judy鈥檚 case.