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I got C from using the Percentile Location formula but the answer is B. The Answer does not even use the formula and just says 21 is the eighth number so thats the answer. I cant understand why they did it this way and even if they did it right. Any thoughts on why they didnt use the formula (N+1) * (Y/100)?
i dont see anything wrong in the answer. You have to find the fourth quintile. Remember to arrange the data in ascending order before proceeding with the solution. Now the distribution is divided into fifths. Therefore, first quintile has two numbers, ie -11 and -5. Second quintile again has two numbers, i.e 8 and 9. Similarly third has 18 and 20, fourth has 20, 21 and lastly fifth has 25 and 35. Now out of the given choices i find only 21 to be the correct one. Hope I made myself clear. And you dont need to use the formula here, it can be solved like this.
I dont see your logic of not using the formula?
I always thought you use the formula to claucalte the location
*calculate
Hi,
In the Schwesser you have it explained on the page 173, at least my version…
You can use the equation, when the effect of multiplying gives you some rounding number not total one, here it’s total i.e. 10*80/100 = 8…and 8 is 21, that’s it.
but the percentile formula uses (n+1) so it would be 11 observations.
@letscookbreakfast Exactly. Thats what is confusing me. I did it that way and got the wrong answer.
BUMP
if you are gettig total number don’t use the formula…
@Czempijan What if the total number of samples were 10 and we had to find median? Then we would get wrong answer if we followed your advice (even in this case we will be getting a whole number)
of course you would get wrong answer finding median…but this is different story, right ---- we are talking about percentiles here…