How to Draw a QQ Plot (Normal Quantile Plot) Using Excel

[sirjoaq]

Whats the meaning of resting 0.5 to each position and then divide it by the N in the percentile formula?I can not get whats the specific meaning of 0.5, is it related to percentile instead of any other quantile?

[fg]

Is the rank really just the ordinal number or is it the rank in the mathematical sense, the arithmetic mean of the ordinal numbers?
So instead of giving the two 67s in the beginning rank 1 and 2, they would both get rank 1.5 = (1 + 2) / 2. For that excel provides the function rank().