How do you find the lower quartile of a box and whisker plot and a data set?

Question

 I have homework to do and I don't get how to find the lower and upper quartile with this set of numbers: 18.75 ,31.6 ,34 ,35 ,35.7 ,37.5

Answer 1

You first put the numbers in order from least to greatest

18.75  31.6  34  35  35.7  37.5

 

From there you can find the median (middle number).  Since you have an even amount of numbers in your list, you must find the mean (average) of the 2 middle numbers to find the median.

 

(34 + 35)/ 2 = 34.5 <-------- median

 

To find the lower quartile, you take the numbers smaller than your median and make sure they are listed in order

18.75   31.6    34

 

Now take the median of this set of numbers

 

31.6 <--------- lower quartile

 

To find the upper quartile, you take the numbers larger than your median and make sure they are listed in order

35    35.7    37.5

 

Now take the median of this set of numbers

 

35.7 <----------- upper quartile