I manage to find the perfect match for the answer. Thank anyways - BUT still in CoNfUsIoN - is it from the BOOK or the MIND? !!!
The solution is very easy to reach, but the question is HARD to understand clearly, lacking precision maybe.
My work-out solution on the graph above is WRONG: I divide 30/12 = 2.5 - infact it is referring to 12 th value not 12 divisions.
QUESTION IS: ESTIMATE THE 12TH HIGHEST SALINITY LEVEL.
so, What Should I understand by that?
1. The 12th highest value could simply be the 12th value of the first 12 values at the beginning of the distribution. ( 12 match with ≈ 10.3)
2. It could be just the highest value of the last top 12 highest values or the highest value of the distribution itself. (30 match with ≈ 15.95)
3. And less likely to be the least value of the last top 12 highest values or the first value of the last top 12 highest values of the distribution
(30 -12 = 18 match with ≈ 11.4 Book Given Answer :!)
Maybe the Question should be : ESTIMATE THE 18th HIGHEST SANITY LEVEL,
or could it be an error in the original question,
or that it is us who is mistaken?
In a hurry, one could have taken any one of these 2 first possibilities as answer, and less likely the 3rd one.
Hope someone else could give the last and best explanation here .
* I suggest you work out that simple statistics question on graph on your own and comment about the answer you get, thank again.