I'm trying ti calculate the first and third quartile for this number set, but all my sources are giving me different answers. Here is the data set.

5000000
5300000
5600000
5900000
6100000
6600000

I've been using the calculator on this site to check my answers,http://www.alcula.com/calculators/statis…

When I use Excel for the first quartile it gives me the number 5375000. But the website gives me 5225000. When I try and calculate it myself I also get 5225000.

But then when I go to calculate the third quartile, the website gives me 6225000 and Excel gives me 6050000. When I check this one with my own calculations it gives me 6050000.

First my calculations supported what the website says, but for the third quartile it matches what Excel gives me. Can anybody please give me any kind of insight as to why this is happening? And more importantly, what the real quartiles are and how I arrive at them in the future?

I am really terrible at math, but I'm also super concerned about my grades, so I've been stressing a lot about this. Any help I can get is much appreciated!