Confused by Quartile Calculation? Get Help Here!

[ojsimon]

Normally this is a very easy task, but i just can't get this one right.

the data set is 14
14
14
15
15
15
15
15
15
16
16
16
16
16
16
17
17
17
18
25

And i get Q1 and Q2 right at 15 and 16, but i keep getting the upper quartile as 17, when it is meant to be 16.5. Can anyone help me as to how to get this answer?

Thanks

 

[mathman]

You have 20 items. The upper quartile is between the fifth and sixth item counting from the top. These are 17 and 16 respectively.