KomalSg wrote:
The heights of boys in a school are normally distributed. Boy1's height is at 80th percentile. Boy2's height is at 20th percentile.
Quantity A |
Quantity B |
Percentage of students whose heights are less than or equal to Boy 1's height |
Percentage of students whose height are more than Boy 2's height. |
A)The quantity in Column A is greater.
B)The quantity in Column B is greater.
C)The two quantities are equal.
D)The relationship cannot be determined from the information given.
Would the answer be C or A?
Let's say there are
100 students in the school.
If Boy 1's height is in the 80th percentile, then if we arrange all of the heights in
ascending order, Boy 1's height will be the 81st value.
Since 80 heights are less than Boy 1's height, this means Boy 1's height is in the 80th percentile. If Boy 2's height is in the 20th percentile, then if we arrange all of the heights in
ascending order, Boy 2's height will be the 21st value.
Since 20 heights are less than Boy 2's height, this means Boy 2's height is in the 20th percentile. Quantity A: Percentage of students whose heights are less than OR EQUAL TO Boy 1's height
If we arrange all of the heights in
ascending order, Boy 1's height will be the 81st value, which means there are
81 students whose heights are less than
or equal to Boy 1's height.
In other words,
81 percent of students have heights that are less than
or equal to Boy 1's height.
Quantity B: Percentage of students whose height are more than Boy 2's height.
Important: Quantity A featured the words "or equal to," whereas Quantity B does not have those same words.
If we arrange all of the heights in
ascending order, Boy 2's height will be the 21st value.
100 - 21 = 79. So, there are
79 students whose heights are greater than Boy 2's height.
In other words,
79 percent of students have heights that are greater than Boy 2's height.
Answer: A
Cheers,
Brent
Sorry if it is a repeating question, but it is something that always confuses me.
If there are 100 students. Why the 80th percentile student is the 81 student and not the 80 student?
I assume it is because of the even/odd area, but maybe you can explain it in a better way?