Problems in calculating quartiles,median, etc etc

[vicky_cool400]

Guys
i am facing lots of problems in calculating median,quartiles , percentiles etc etc
I mean in o=some question we use only N in numerator and in some we take N+1 .
Please tell when to use which forumula

 

[birdec]

Use this formula: (n+1)*(quartile %/100)
Sort the data in ascending order. n = the number of data points
If you’re looking for the 3rd quartile you would put in: (16+1)*(75/100) and you get some answer
That answer is the number of data points you have to count up the list of data
So if you got an answer of 12.75 for example you would count up 12 data points and get a data point of 54 lets say. In order to capture that “.75” portion of 12.75 you add the difference of the next number minus 54 (our fictional 12th data point) and multiply it by 75/100. So if the next number was 87 it would look like this:
54 + (87-54) * (75/100) = 78.75… 78.75 would be the third quartile of our data set

 

[vicky_cool400]

ok so we will always use N+1 in numerator ?