Question 729177
 box and whisker 71,74,74,75,75,77,77,78,78,80,80,81,82,86,86,90

first find the median: The median is the value exactly in the middle of an ordered set of numbers.

so, the median is {{{78}}}

 Next, we consider only the values to the left of the median: 71,74,74,75,75,77,77. 

We now find the median of this set of numbers. Remember, the median is the value exactly in the middle of an ordered set of numbers.
 
Thus {{{75}}} is the median of the scores less than the median of all scores, and therefore is the lower quartile.

{{{75}}} is the lower quartile

Now consider only the values to the right of the median: 78 82 85 87 91 93 100. We now find the median of this set of numbers. The median {{{82}}} is therefore called the upper quartile.

{{{82}}} is the upper quartile

    You are now ready to find the inter-quartile range (IQR). The inter-quartile range is the difference between the upper quartile and the lower quartile. 

In your case the {{{IQR = 82 - 75 = 7}}}. 

The IQR is a very useful measurement. It is useful because it is less influenced by extreme values, it limits the range to the middle 50% of the values.

{{{7}}} is the inter-quartile range

Now you can draw your graph.