Understanding Percentiles: Solving MCQ Homework

  • Thread starter Thread starter UNknown 2010
  • Start date Start date
  • Tags Tags
    Percentile
AI Thread Summary
If 30 percent of a reference group scored higher than you, your score would be at the 70th percentile. This is because the percentile indicates the percentage of scores that fall below a certain value. The discussion clarifies that a score at the 30th percentile means 30 percent scored below that score, while a score at the 70th percentile means 70 percent scored below it. The confusion arises from misunderstanding the definition of percentiles. Therefore, the correct answer is (b) at the 70th percentile.
UNknown 2010
Messages
77
Reaction score
0

Homework Statement


If a 30 percent of a reference group scored higher than you did on a test, your score would be:
a)at the 30th percentile
b)at the 70th percentile
c)at the 71st percentile
d)at the 29th percentile
e)indeterminate from the available information

Homework Equations


I think it is c ?Please I need fast reply because my exam is very close

The Attempt at a Solution

 
Last edited:
Physics news on Phys.org
What do you think "percentile" means? Why do you think it is c?
 
From wiki
A percentile (or centile) is the value of a variable below which a certain percent of observations fall. So the 20th percentile is the value (or score) below which 20 percent of the observations may be found. The term percentile and the related term percentile rank are often used in descriptive statistics as well as in the reporting of scores from norm-referenced tests. The 25th percentile is also known as the first quartile (Q1); the 50th percentile as the median or second quartile (Q2); the 75th percentile as the third quartile (Q3).

It should be (b) .. isn't it?
 
I tried to combine those 2 formulas but it didn't work. I tried using another case where there are 2 red balls and 2 blue balls only so when combining the formula I got ##\frac{(4-1)!}{2!2!}=\frac{3}{2}## which does not make sense. Is there any formula to calculate cyclic permutation of identical objects or I have to do it by listing all the possibilities? Thanks
Since ##px^9+q## is the factor, then ##x^9=\frac{-q}{p}## will be one of the roots. Let ##f(x)=27x^{18}+bx^9+70##, then: $$27\left(\frac{-q}{p}\right)^2+b\left(\frac{-q}{p}\right)+70=0$$ $$b=27 \frac{q}{p}+70 \frac{p}{q}$$ $$b=\frac{27q^2+70p^2}{pq}$$ From this expression, it looks like there is no greatest value of ##b## because increasing the value of ##p## and ##q## will also increase the value of ##b##. How to find the greatest value of ##b##? Thanks
Back
Top