SOLUTION: What proportion of the data is between the first and third quartiles?

Question 390733: What proportion of the data is between the first and third quartiles?
Found 3 solutions by rfer, richard1234, robertb:
Answer by rfer(16322)   (Show Source): You can put this solution on YOUR website!
2nd quartile= 25%
Or do you want from the 1st through the 3rd?
That = 75%
Answer by richard1234(7193)   (Show Source): You can put this solution on YOUR website!
If it's strictly between the first and third quartile, then you're talking about the second quartile, or 25%. If it's between the first and third quartiles, inclusive, then it's 75% of the data.
Answer by robertb(5830)   (Show Source): You can put this solution on YOUR website!
The 1st quartile Q1 demarcates the lowest 25% of the distribution from the higher 75%.
The 3rd quartile Q3 demarcates the lower 75% of the distribution from the highest 25%.
(We are assuming here that the values of the RV are either in increasing or decreasing order.)
What is in between the Q1 and Q3 then, is exactly 50% of the distribution. (Think of it this way: Exclude the lowest 25% of the distribution and the highest 25% of the distribution and you get exactly the middle 50% of the distribution.)
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