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Re: The 75th percentile on a test corresponded to a score of 700 [#permalink]
"750 could be the 95th percentile score—or 963 could be"

How did you get these limits ? Can you please elaborate?
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Re: The 75th percentile on a test corresponded to a score of 700 [#permalink]
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You should deserve more than a kudo Sir., for the amazing , spot-on explanations.

Regards
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Re: The 75th percentile on a test corresponded to a score of 700 [#permalink]
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GreenlightTestPrep wrote:
sandy wrote:
The 75th percentile on a test corresponded to a score of 700, while the 25th percentile corresponded to a score of 450.

Quantity A
Quantity B
A 95th percentile score
\(800\)


A) Quantity A is greater.
B) Quantity B is greater.
C) The two quantities are equal.
D) The relationship cannot be determined from the information given.


IMPORTANT: Many students will assume that the above distribution of scores is a NORMAL distribution.
However, since this is not mentioned, we can't assume that we have a normal distribution.
This means the scores don't follow any particular pattern (as in a normal distribution)

To begin, let's say there are 100 scores in TOTAL.

NOTE:
If a score of 450 is in the 25th percentile, then 25 scores are less than 450, and...
If a score of 700 is in the 75th percentile, then 75 scores are less than 700

So, it COULD be the case that, when arranged in ASCENDING order, the first 76 value are as follows:
{1,1,1,...(25 1's in total),...1,1,1,450,451,451,451,...(49 451's in total),451,451,451,451...700.....}

The 76 values above satisfy the given information.

The remaining 24 scores can be pretty much anything (as long as they're greater than 700)

So, it COULD be the case that the next 19 values are 701
{1,1,1,...(25 1's in total),...1,1,1,450,451,451,451,...(49 451's in total),451,451,451,451...700, 701,701,701,701,701,701,701,701,701,701,701,701,701,701,701,701,701,701,701, .....}

At this point, we've listed 95 of the 100 values.
So, the next value in the list will be the 95th percentile score.

Consider these two possible cases:

case i: The values are:
{1,1,1,...(25 1's in total),...1,1,1,450,451,451,451,...(49 451's in total),451,451,451,451...700, 701,701,701,701,701,701,701,701,701,701,701,701,701,701,701,701,701,701,701, 702.....}
In this case, 702 is the 95th percentile score.
Since 702 < 800, Quantity B is greater

case ii: The values are:
{1,1,1,...(25 1's in total),...1,1,1,450,451,451,451,...(49 451's in total),451,451,451,451...700, 701,701,701,701,701,701,701,701,701,701,701,701,701,701,701,701,701,701,701, 1,000,000.....}
In this case, 1,000,000 is the 95th percentile score.
Since 1,000,000 > 800, Quantity A is greater

Answer: D

Cheers,
Brent




Thanks for your explanation.
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Re: The 75th percentile on a test corresponded to a score of 700 [#permalink]
1
GreenlightTestPrep wrote:
sandy wrote:
The 75th percentile on a test corresponded to a score of 700, while the 25th percentile corresponded to a score of 450.

Quantity A
Quantity B
A 95th percentile score
\(800\)


A) Quantity A is greater.
B) Quantity B is greater.
C) The two quantities are equal.
D) The relationship cannot be determined from the information given.


IMPORTANT: Many students will assume that the above distribution of scores is a NORMAL distribution.
However, since this is not mentioned, we can't assume that we have a normal distribution.
This means the scores don't follow any particular pattern (as in a normal distribution)

To begin, let's say there are 100 scores in TOTAL.

NOTE:
If a score of 450 is in the 25th percentile, then 25 scores are less than 450, and...
If a score of 700 is in the 75th percentile, then 75 scores are less than 700

So, it COULD be the case that, when arranged in ASCENDING order, the first 76 value are as follows:
{1,1,1,...(25 1's in total),...1,1,1,450,451,451,451,...(49 451's in total),451,451,451,451...700.....}

The 76 values above satisfy the given information.

The remaining 24 scores can be pretty much anything (as long as they're greater than 700)

So, it COULD be the case that the next 19 values are 701
{1,1,1,...(25 1's in total),...1,1,1,450,451,451,451,...(49 451's in total),451,451,451,451...700, 701,701,701,701,701,701,701,701,701,701,701,701,701,701,701,701,701,701,701, .....}

At this point, we've listed 95 of the 100 values.
So, the next value in the list will be the 95th percentile score.

Consider these two possible cases:

case i: The values are:
{1,1,1,...(25 1's in total),...1,1,1,450,451,451,451,...(49 451's in total),451,451,451,451...700, 701,701,701,701,701,701,701,701,701,701,701,701,701,701,701,701,701,701,701, 702.....}
In this case, 702 is the 95th percentile score.
Since 702 < 800, Quantity B is greater

case ii: The values are:
{1,1,1,...(25 1's in total),...1,1,1,450,451,451,451,...(49 451's in total),451,451,451,451...700, 701,701,701,701,701,701,701,701,701,701,701,701,701,701,701,701,701,701,701, 1,000,000.....}
In this case, 1,000,000 is the 95th percentile score.
Since 1,000,000 > 800, Quantity A is greater

Answer: D

Cheers,
Brent


This was an amazing explanation. I have a small request, just to make my concept clear.

If I attempt this question assuming the scores have a normal distribution, then this is my thought process,

450 is 25%
700 is 75%

700-450 = 250

As they both are equally around the mean, 50% to 75% = 125



700+125 = 825 is ideally what 100% should be ( for linearly distributed graph)

But since this is a normal distribution,

area covered between 50%-75% > area covered between 75-95%

To make them equal, I will have to shift the 95% to the right, which is > 825

It cannot be determined how much > 825 it is supposed to be, hence answer is still D if the above question is modified to a normal distribution.

Please correct me if my thought process is wrong. Thank you.
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Re: The 75th percentile on a test corresponded to a score of 700 [#permalink]
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It is indeed correct
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Re: The 75th percentile on a test corresponded to a score of 700 [#permalink]
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Carcass wrote:
It is indeed correct


Alright! Thank you
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The 75th percentile on a test corresponded to a score of 700 [#permalink]
1
sandy wrote:
The 75th percentile on a test corresponded to a score of 700, while the 25th percentile corresponded to a score of 450.

Quantity A
Quantity B
A 95th percentile score
\(800\)


A) Quantity A is greater.
B) Quantity B is greater.
C) The two quantities are equal.
D) The relationship cannot be determined from the information given.


It's quite normal to assume that this distribution is normal or could be normalized ...

That a question requires to determine 95 percentile value makes it deficient of all required data to answer the question correctly. Hence, it's a choice D.

25 percentile is between 16 and 50 percentiles
75 percentile is between 50 and 84 percentiles

Therefore minimum value of a standard deviation must be 125 or (700-250)/2

We know that 95 percentile could be equal to 97-98 percentiles (or two standard deviations from the defined mean) or below 97-98 percentiles. It's not quaranteed; otherwise 97-98 percentile is definitely above 800 (=700+125). But here, do not have sufficient information to answer this question correctly.

Answer is D
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Re: The 75th percentile on a test corresponded to a score of 700 [#permalink]
sandy wrote:
The 75th percentile on a test corresponded to a score of 700, while the 25th percentile corresponded to a score of 450.

Quantity A
Quantity B
A 95th percentile score
\(800\)


A) Quantity A is greater.
B) Quantity B is greater.
C) The two quantities are equal.
D) The relationship cannot be determined from the information given.


Posted from my mobile device
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Re: The 75th percentile on a test corresponded to a score of 700 [#permalink]
Since the information about the distribution of scores is not given, the relationship can't be determined. If the distribution of scores was stated as the uniform distribution, the answer would be C. If the distribution of scores was stated as the normal distribution, the answer would be A.
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The 75th percentile on a test corresponded to a score of 700 [#permalink]
Since the information about the distribution of scores is not given, the relationship can't be determined. If the distribution of scores was stated as the uniform distribution, the answer would be C. If the distribution of scores was stated as the normal distribution, the answer would be A.
To answer the question, we need to know its distribution type since percentiles depend on the distribution.
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Re: The 75th percentile on a test corresponded to a score of 700 [#permalink]
dobby wrote:
GreenlightTestPrep wrote:
sandy wrote:
The 75th percentile on a test corresponded to a score of 700, while the 25th percentile corresponded to a score of 450.

Quantity A
Quantity B
A 95th percentile score
\(800\)


A) Quantity A is greater.
B) Quantity B is greater.
C) The two quantities are equal.
D) The relationship cannot be determined from the information given.


IMPORTANT: Many students will assume that the above distribution of scores is a NORMAL distribution.
However, since this is not mentioned, we can't assume that we have a normal distribution.
This means the scores don't follow any particular pattern (as in a normal distribution)

To begin, let's say there are 100 scores in TOTAL.

NOTE:
If a score of 450 is in the 25th percentile, then 25 scores are less than 450, and...
If a score of 700 is in the 75th percentile, then 75 scores are less than 700

So, it COULD be the case that, when arranged in ASCENDING order, the first 76 value are as follows:
{1,1,1,...(25 1's in total),...1,1,1,450,451,451,451,...(49 451's in total),451,451,451,451...700.....}

The 76 values above satisfy the given information.

The remaining 24 scores can be pretty much anything (as long as they're greater than 700)

So, it COULD be the case that the next 19 values are 701
{1,1,1,...(25 1's in total),...1,1,1,450,451,451,451,...(49 451's in total),451,451,451,451...700, 701,701,701,701,701,701,701,701,701,701,701,701,701,701,701,701,701,701,701, .....}

At this point, we've listed 95 of the 100 values.
So, the next value in the list will be the 95th percentile score.

Consider these two possible cases:

case i: The values are:
{1,1,1,...(25 1's in total),...1,1,1,450,451,451,451,...(49 451's in total),451,451,451,451...700, 701,701,701,701,701,701,701,701,701,701,701,701,701,701,701,701,701,701,701, 702.....}
In this case, 702 is the 95th percentile score.
Since 702 < 800, Quantity B is greater

case ii: The values are:
{1,1,1,...(25 1's in total),...1,1,1,450,451,451,451,...(49 451's in total),451,451,451,451...700, 701,701,701,701,701,701,701,701,701,701,701,701,701,701,701,701,701,701,701, 1,000,000.....}
In this case, 1,000,000 is the 95th percentile score.
Since 1,000,000 > 800, Quantity A is greater

Answer: D

Cheers,
Brent


This was an amazing explanation. I have a small request, just to make my concept clear.

If I attempt this question assuming the scores have a normal distribution, then this is my thought process,

450 is 25%
700 is 75%

700-450 = 250

As they both are equally around the mean, 50% to 75% = 125



700+125 = 825 is ideally what 100% should be ( for linearly distributed graph)

But since this is a normal distribution,

area covered between 50%-75% > area covered between 75-95%

To make them equal, I will have to shift the 95% to the right, which is > 825

It cannot be determined how much > 825 it is supposed to be, hence answer is still D if the above question is modified to a normal distribution.

Please correct me if my thought process is wrong. Thank you.



why is ans d in this case shouldn't it be a if it is normaly distributed
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Re: The 75th percentile on a test corresponded to a score of 700 [#permalink]
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sorry what is specifically unclear in the brent's explanation?
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Re: The 75th percentile on a test corresponded to a score of 700 [#permalink]
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