Hello Guys I believe there is a mistake in question id 1745. Problem: What are the median and the third quintile of the following data points? 9.2% 10.1% 11.5% 11.9% 12.2% 12.8% 13.1% 13.6% 13.9% 14.2% 14.8% 14.9% 15.4% Qbank solution is 13.1% median and third quintile is 13.7% Qbank interpolation is: 0.136 + (o.4)(0.139-0.136)= o.1372 =>13.7% My solution is: 0.136 + (0.6 due to third quintile)(0.139-0.136) = 0.1378 => 13.8%, but not given as one of the solution options. third quintile is 0.6. ------------------------------------------------------------------------------------------------------------- Feedback welcomed 
I would have thought it to be 13.7 as well. Arriving this way: (n+1)(3/5) = (13+1)*3/5 = 8.4 8th is .136 0.4th is (0.4)(0.139-0.136) I think you are trying to use 0.6 directly in the linear interpolation.
For finding the solution, You are rite, median is 13.1%. Now, For finding quintile, it is Ly= ((n+1)*y)/100; so here y=75%. It is coming out as 10.6 so it will be, 14.2+ 0.6*(14.8-14.2)=14.56. So third quantile will be 14.56.
Yes no doubt…but why are you using 0.4 in the interpolation instead 0.6? I used 0.6 because 3/5 = 0.6 How are you getting 0.4 to calculate L?
Prasenjith your way is right, but y = 60% in this question and not 75% 
But you used just like I did 0.6 as y. y =0.6 Thanks for all the replies
I am using 0.4 because I arrived at 8.4 ; that is the 0.4 fractions from the 8th to 9th element. When calculating 8.4, you have already used the 3/5 logic.
Yes Guys, I did a mistake…I thought it to be 1/4 th part…I have not seen as quintile…sorry…it will be 60%( 100*3/5)… And then ratio will be Ly= (14*(60))/100 =8.4( hope I pressed calculator accurately) In that case it will be =13.6+0.4(13.9-13.6) =13.72 (hope I pressed calculator accurately Thanks a lot
Ok thank you very much you both. I understand it now. the 0.4 is taken from the 8.4 and used for the interpolation and not the 60% ;). 13.72 is correct! Once again thanks for the help.