<PRE><B>Question 358869</B>
Arrange the sample numbers in order: &lt;br&gt;

520 570 600 610 650 670 690 730&lt;br&gt;

The median is 630 which is found by {{{(610+650)/2}}}&lt;br&gt;

The median is also the 50th percentile.&lt;br&gt;

The first quartile (or lower quartile or 25th percentile) is the median of the bottom half of the numbers.  Since there are 8 numbers, the bottom half is the first 4 numbers.&lt;br&gt;

The median of the first 4 numbers is 585 which is found by {{{(570+600)/2}}}&lt;br&gt;

The third quartile (or upper quartile or 75th percentile) is the median of the top half of the numbers.  Since there are 8 numbers, the top half is the last 4 numbers.&lt;br&gt;

The median of the last 4 numbers is 680 which is found by {{{(670+690)/2}}}&lt;br&gt;

The interquartile range is simply the third quartile minus the first quartile.&lt;br&gt;

{{{IQR=680-585}}} or {{{IQR=95}}}&lt;br&gt;

First quartile is 585&lt;br&gt;

Third quartile is 680&lt;br&gt;

Interquartile range is 95&lt;br&gt;

I hope this helps!&lt;br&gt;</PRE>