Posted by **Denim** on Monday, March 5, 2007 at 12:25am.

Can someone help me figure this out?

1. Find the first and third quartiles, Q1 and Q3 of the following numbers:

347,242,146,391,249,567,277,218,319

and

0.16,0.08,0.27,0.20,0.22,0.32,0.25,0.18,0.28,0.27

2. Which of the following numbers are integers?

75,9.82,-1/14,-498,0.71

The calculation of the quartiles is sometimes not quite clear (especially if the number of observations of a sample is not divisible by four). We therefore provide exact instructions how to calculate the quartiles. Assuming a sample of N observations the quartiles are defined as follows ("round" stands for the rounding to the nearest integer):

1. quartile: the value of the sorted series of observations having the position x = round(0.25*(N+1))

2. quartile (median): if N is even, Q2 is the mean of the two values at the positions N/2 and N/2+1; if N is odd, Q2 is the value at the position (N+1)/2

3. quartile: the value of the sorted series having the position x = round(0.75*(N+1))

Example: