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CR - The proportion of minorities....

by scoowhoop » Fri Apr 09, 2010 3:36 pm
Can someone help me understand (algebraically) why D is the answer here? I know the approach is to treat this as a "weaken" question but I'm having a hard time understanding what exactly is being said in the stimulus.

This is from the Vertitas Prep CR2 booklet.
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by Phirozz » Fri Apr 09, 2010 10:14 pm
IMO NONE OF THESE
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by pops » Sat Apr 10, 2010 2:03 am
We are given that:

A: (Minority Home Owner)/(All Home Owner) for given 2 years are equal

Also, given is (Minority Home Owner)/(Minorities) for given 2 years
Now, to deduce A none of the option is helping us.. IMO closest we can get is E.. still insufficient in my opinion
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by ayushiiitm » Sat Apr 10, 2010 5:15 am
scoowhoop wrote:Can someone help me understand (algebraically) why D is the answer here? I know the approach is to treat this as a "weaken" question but I'm having a hard time understanding what exactly is being said in the stimulus.

This is from the Vertitas Prep CR2 booklet.
I just applied the POE technique

A:keep for the moment
B: Would make no difference if we know that fact
C: property value-out of scope
D : non-minority-out of scope
E: non-minority+ apartment-out of scope

So I would settle down for A

What is the OA
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by scoowhoop » Sat Apr 10, 2010 9:00 am
The OA is D.
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by ayushiiitm » Sat Apr 10, 2010 11:23 am
Sorry had misread an important point before. Now I will try showing you a systematic approach

See B,C and E are totally out of scope
B: minorities to own home
C: property value increases
E: apartment

Now to decide between A and D, we should go with a approach and that is to make a map

Conclusion: Proportion of minorities that own their home has remain unchanged
Premise given: 2 given percentages are still same during the given 25 year period

Now see how we put this algebrically
We have two kind of people: Minority and Non minority
We have three kind of houses: owned by minority, owned by non minority and owned by none(may be rented or same ppl own a number of houses)

So to know if the proportion for minorities has to be checked, it is needed that we know how the proportion for non minorities have changed.

Consider it like this

Initially Minority:44.6, Non minority: 20( assuming), none (34.4) >>>total 100%
Now Minority:44.8, Non minority:X, none(100-X)>>total has to remain 100%

So we need X


That makes up for the answer D

Let me know if I am able to make u understand. Would make me happy :)
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by scoowhoop » Sat Apr 10, 2010 11:49 am
I am still very much confused about the Proportion vs. Percent.

Proportion of minorities among families
vs.
Percent of minority working families

I don't see the correlation here!
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by ayushiiitm » Sat Apr 10, 2010 1:08 pm
scoowhoop wrote:I am still very much confused about the Proportion vs. Percent.

Proportion of minorities among families
vs.
Percent of minority working families

I don't see the correlation here!
See working and non working is not taken as a differentiator here....because working appears in options
But its a very good habit that you keep an eye on such a factor.

For Proportion v/s percent

Proportion is a ratio of parts of X in total(Y)
When Y is scaled to a value of 100, X is expressed as percentage

for example:
X=25 and y=50
so proportion of X in Y=25/50 =1/2
percentage of X is when Y is taken as 100
so X comes out to be 50%

See Ill put it simply

Proportion is a ratio of two things. Percentage is that proportion expressed on a scale of 100.

If percentage is 50....then proportion is expressed as 1/2 (multiply it by 100 and you get percentage)

P.S Do what I explained using a pen and paper

And Do let me know if you have difficulty. Ill be glad
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by Phirozz » Sat Apr 10, 2010 7:23 pm
ayushiiitm wrote:
Consider it like this

Initially Minority:44.6, Non minority: 20( assuming), none (34.4) >>>total 100%
Now Minority:44.8, Non minority:X, none(100-X)>>total has to remain 100%

So we need X
Let me know if I am able to make u understand. Would make me happy :)
Plz have a look at ur explanations..

Does the passage anywhere says 44.6% or 44.8% is the house owned by minorities out of the total house owned by families ??

44.8% is the minority families who own their house out of the total minority familieis.

Let say, total minority families were 100 in both 1978 and 2003. So number of houses owned by minority families in both years is around 45

But unless we know the total number of houses owned by nonminority families, proportion cannot be found. I mean knowing only OPTION D is not going to help in calculating proportion.

We need absolute number of nonminority families who owned houses in both the years. Because let say %age of nonminority families who own their house is 50%. But if the total number of nonminority families is 1000(assumed), 500 own their own house. But if the total number of nonminority families is 2000, 50% will give 1000. And this 500 or 1000 which cannot be determined exactly from any of the options have a bearing on calculating %age of minorities among families that owned their own house.

Therefore ANS is NONE OF THE OPTIONS.
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by liferocks » Sat Apr 10, 2010 9:11 pm
qs says proportion of minorities among families that own their house is unchanged.
that means we have
minority families that own their house/non-minority families that own their house
is unchanged
now we know that 44% of minority family own their house ie 44 among 100 own the house
so to calculate the proportion we need to know the denominator ie how many among non minorities own the house

only option D gives the ans
so OA is D

to re phrase this x among 100 own house for minority and y among 100 own house for non-minority since base in both case is 100 we can conclude that proportion is X/Y here x is present but Y missing..so we need the Y
I hope my reasoning is correct..please point out any mistake you see so that we can re evaluate.
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by Phirozz » Sat Apr 10, 2010 10:50 pm
liferocks wrote:qs says proportion of minorities among families that own their house is unchanged.
that means we have
minority families that own their house/non-minority families that own their house
is unchanged
now we know that 44% of minority family own their house ie 44 among 100 own the house
so to calculate the proportion we need to know the denominator ie how many among non minorities own the house

only option D gives the ans
so OA is D

to re phrase this x among 100 own house for minority and y among 100 own house for non-minority since base in both case is 100 we can conclude that proportion is X/Y here x is present but Y missing..so we need the Y
I hope my reasoning is correct..please point out any mistake you see so that we can re evaluate.
Look at the bold parts, proportion of minorities among families that own their own house means
house owned by minority families/total house owned by both minority and nonminority families.
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by liferocks » Sat Apr 10, 2010 11:25 pm
Phirozz wrote:
liferocks wrote:qs says proportion of minorities among families that own their house is unchanged.
that means we have
minority families that own their house/non-minority families that own their house
is unchanged
now we know that 44% of minority family own their house ie 44 among 100 own the house
so to calculate the proportion we need to know the denominator ie how many among non minorities own the house

only option D gives the ans
so OA is D

to re phrase this x among 100 own house for minority and y among 100 own house for non-minority since base in both case is 100 we can conclude that proportion is X/Y here x is present but Y missing..so we need the Y
I hope my reasoning is correct..please point out any mistake you see so that we can re evaluate.

Look at the bold parts, proportion of minorities among families that own their own house means
house owned by minority families/total house owned by both minority and nonminority families.
thanks for correcting me..but in that case we will need X/(X+Y) whereX is number of minority family owning home and Y is number of non minority family owning home.
So in this case as well only unknown thing is Y..which option D tells
so option D is correct.
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by Phirozz » Sun Apr 11, 2010 12:09 am
liferocks wrote:
thanks for correcting me..but in that case we will need X/(X+Y) whereX is number of minority family owning home and Y is number of non minority family owning home.
So in this case as well only unknown thing is Y..which option D tells
so option D is correct.
D gives only %age and not absolute figure

Let say there are 100 minority families in both of these year. 44 out of 100.

Now let say number of nonminority families 100 and 50%(assumed) own their own house.
So proportion of minorities among those who own their own house is 44/94

Lets assume another instance where number of nonminority who own house is 1000 but the %age remains same as 50%
Here, proportion of among those who own their own house is 44/544

44/94 is not equal to 44/544. So knowing only %age will not help us. We need absolute numbers
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by lunarpower » Fri Apr 16, 2010 8:37 pm
this is actually a pretty bad question -- even with the information given in the "correct" answer choice (d), we still wouldn't have enough information to judge the claim made in the passage.

for instance, consider a situation in which the percentages given in the passage hold, and, to satisfy the requirements of choice (d), let's postulate that exactly the same percentages of nonminorities also owned homes in those two years (i.e., 44.6% and 44.8%).

even with this information, we would still have absolutely no idea about the statistic in question (i.e., the percentage OF families who own homes that are minorities).

we can't make this judgment without information about the actual sizes of the populations under examination.
viz., if there are many more minorities than non-minorities, then the vast majority OF families who own homes will be minorities, despite the identical percentages within each group. also, vice versa.
Ron has been teaching various standardized tests for 20 years.

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by lunarpower » Fri Apr 16, 2010 8:38 pm
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still, even though this question is unacceptable by the standards of the gmat, we can still eliminate down to the correct answer:

* (a) doesn't help at all, since we already have that statistic (we would just have to subtract the given percentages from 100%).

* not only is (b) irrelevant (we don't care if the families who owned homes in 1978 were the same ones who owned homes in 2003), but it's not even a proper answer to the prompt: this is not a statistic "with regard to which we can compare 1978 and 2003", as required in the prompt.
in other words, the prompt absolutely demands a statistic that has SEPARATE VALUES for 1978 and 2003. since this one doesn't (it's a single value, taking both of those years into account), it's impossible that this could be the correct answer.

* (c) and (e) discuss topics that are clearly irrelevant to the passage.

that leaves (b), which, although not a good enough answer by the standards of the official test, is nonetheless the "best" answer in the question at hand.
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