Measures of Dispersion

1. The standard deviation of the amounts is $s_{x} \approx 2.55$ gigabytes.

2. The standard deviation is

$s_{x}=\sqrt{\dfrac{(21-47)^{2}+(28-47)^{2}+\cdots+(70-47)^{2}}{7}}\$

3. Jerry's error is that his denominator is incorrect.

4. The standard deviation of the times is $s_{x} \approx 3.24$ minutes.