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# The median annual household income in a certain community of

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The median annual household income in a certain community of [#permalink]

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21 Jun 2008, 20:01
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The median annual household income in a certain community of 21 households is $50,000. If the mean income of a household increases by 10% per year over the next 2 years, what will the median income in the community be in 2 years? (A)$50,000
(B) $60,000 (C)$60,500
(D) $65,000 (E) Cannot be determined [Reveal] Spoiler: OA _________________ GMAT the final frontie!!!. Last edited by Bunuel on 12 Aug 2012, 07:17, edited 1 time in total. Edited the question and added the OA. SVP Joined: 04 May 2006 Posts: 1926 Schools: CBS, Kellogg Followers: 22 Kudos [?]: 985 [0], given: 1 Re: Median [#permalink] ### Show Tags 21 Jun 2008, 20:44 alimad wrote: The median annual household income in a certain community of 21 households is$50,000. If the mean income of a household increases by 10 % / year over the next 2 years, what will be the median income in the community be in 2 years?

50,000
60,000
60,500
65,000
cannot be determined.

I think E, I find no connection btw the increase and the median!
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21 Jul 2008, 10:45
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sondenso wrote:
The median annual household income in a certain community of 21 households is $50,000. If the mean income of a household increases by 10 % / year over the next 2 years, what will be the median income in the community be in 2 years? 50,000 60,000 60,500 65,000 cannot be determined. Please respond with your answers. thanks I think E, I find no connection btw the increase and the median! I agree on E. The median could change depending on which incomes grow and by how much. For example, all incomes could grow by 10% each, meaning the median would also grow by 10%. Or the lowest income could grow by a huge number, moving it into the top half of incomes, which would completely change the median. Senior Manager Joined: 06 Apr 2008 Posts: 449 Followers: 1 Kudos [?]: 137 [1] , given: 1 Re: Median [#permalink] ### Show Tags 21 Jul 2008, 22:19 1 This post received KUDOS Should be e) Mean increasing by certain % doesnt mean that median should increase by same %. Median will only increase by same % if all data point move ahead by same % but increase of mean does not guarantee that all data points are moving by same % as well. Manager Joined: 04 Dec 2011 Posts: 81 Schools: Smith '16 (I) Followers: 0 Kudos [?]: 20 [0], given: 13 Re: Median [#permalink] ### Show Tags 12 Aug 2012, 07:08 nmohindru wrote: Should be e) Mean increasing by certain % doesnt mean that median should increase by same %. Median will only increase by same % if all data point move ahead by same % but increase of mean does not guarantee that all data points are moving by same % as well. Hi, I am a bit confused now, I thought this was the rule.. " If we increase or decrease each term in a set by the same percent: Mean will increase or decrease by the same percent. SD will increase or decrease by the same percent. so by that if mean increase by 10%, shouldn't all data points move by 10%..? By the way, above rule was also Highlighted in one of the post by Bunuel Here ps-questions-about-standard-deviation-85897.html am I missing a point here? can someone please explain the concept here? _________________ Life is very similar to a boxing ring. Defeat is not final when you fall down… It is final when you refuse to get up and fight back! 1 Kudos = 1 thanks Nikhil Math Expert Joined: 02 Sep 2009 Posts: 35932 Followers: 6860 Kudos [?]: 90100 [3] , given: 10413 Re: Median [#permalink] ### Show Tags 12 Aug 2012, 07:27 3 This post received KUDOS Expert's post 4 This post was BOOKMARKED nikhil007 wrote: nmohindru wrote: The median annual household income in a certain community of 21 households is$50,000. If the mean income of a household increases by 10% per year over the next 2 years, what will the median income in the community be in 2 years?

(A) $50,000 (B)$60,000
(C) $60,500 (D)$65,000
(E) Cannot be determined

Should be e)

Mean increasing by certain % doesnt mean that median should increase by same %.

Median will only increase by same % if all data point move ahead by same % but increase of mean does not guarantee that all data points are moving by same % as well.

Hi,

I am a bit confused now,

I thought this was the rule..
" If we increase or decrease each term in a set by the same percent:
Mean will increase or decrease by the same percent.
SD will increase or decrease by the same percent.

so by that if mean increase by 10%, shouldn't all data points move by 10%..?

By the way, above rule was also Highlighted in one of the post by Bunuel Here

am I missing a point here? can someone please explain the concept here?

Reverse of this property is not true: if the mean increases by a certain percent it doesn't necessarily mean that each term increases by the same percent.

Consider the following set: {1, 2, 3} --> mean=median=2 and sum=6. Now, if we increase the mean by 100%, we increase the sum by 100%, so it'll become 12. But new set can be {0, 0, 12}: the third element increased and the first two elements decreased or {2, 2, 8}: the first and the third elements increased and the second remained the same...

You can apply the same logic to the question at hand.

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12 Aug 2012, 23:34
Bunuel wrote:

Reverse of this property is not true: if the mean increases by a certain percent it doesn't necessarily mean that each term increases by the same percent.

Consider the following set: {1, 2, 3} --> mean=median=2 and sum=6. Now, if we increase the mean by 100%, we increase the sum by 100%, so it'll become 12. But new set can be {0, 0, 12}: the third element increased and the first two elements decreased or {2, 2, 8}: the first and the third elements increased and the second remained the same...

You can apply the same logic to the question at hand.

Wow thats an usefull insight..Kudos..!!
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Re: The median annual household income in a certain community of [#permalink]

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16 Aug 2012, 21:48
Answer is E, because there are different numbers in the set and we are not sure which side of the numbers in the set will be increased so the mean is increase by 10%. It could be the case that small number of higher end incomes increased a little or many low end incomes increased - it cannot be identified.
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Re: The median annual household income in a certain community of [#permalink]

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18 Aug 2012, 17:55
+1 E

For example, if the highest value increase enough to increase in 10% the mean, the median will be the same.
Other scenario is that every value increases in 10%, including the median.
We cannot determine the new median.
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Re: The median annual household income in a certain community of [#permalink]

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15 Apr 2014, 12:34
But here the It is clearly mentioned that it is the mean income of a household..So here the mean refers to the average rise in income of the household members and not the mean of the incomes of the cimmunity..I think it is a typo error or I am missing something here...
Correct me if I am wrong
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Re: The median annual household income in a certain community of [#permalink]

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15 Apr 2014, 12:47
JusTLucK04 wrote:
But here the It is clearly mentioned that it is the mean income of a household..So here the mean refers to the average rise in income of the household members and not the mean of the incomes of the cimmunity..I think it is a typo error or I am missing something here...
Correct me if I am wrong

We can not determine the median income from provided data.

The median annual household income in a certain community of 21 households is $50,000. If the mean income of a household increases by 10% per year over the next 2 years, what will the median income in the community be in 2 years? As we do not know that distribution of income is uniform we can not conclude that median = mean from provided data we got that 11th household is earning$50,000
Let mean = x increase by 10% for next 2 years... we do not whether every house hold income has increased or few has increased or for few remain constant or reduced.. its easy to get 10% rise in mean by just increasing income for few households ..thus we can not construct data set and we can not get median.

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Re: The median annual household income in a certain community of [#permalink]

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15 Apr 2014, 12:57
PiyushK wrote:
JusTLucK04 wrote:
But here the It is clearly mentioned that it is the mean income of a household..So here the mean refers to the average rise in income of the household members and not the mean of the incomes of the cimmunity..I think it is a typo error or I am missing something here...
Correct me if I am wrong

We can not determine the median income from provided data.

The median annual household income in a certain community of 21 households is $50,000. If the mean income of a household increases by 10% per year over the next 2 years, what will the median income in the community be in 2 years? As we do not know that distribution of income is uniform we can not conclude that median = mean from provided data we got that 11th household is earning$50,000
Let mean = x increase by 10% for next 2 years... we do not whether every house hold income has increased or few has increased or for few remain constant or reduced.. its easy to get 10% rise in mean by just increasing income for few households ..thus we can not construct data set and we can not get median.

Bahh..My bad..I read it extremely wrongly. ...I was referring to the income rise from household members.. Don't know where did that come from..Guess I did better
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Re: The median annual household income in a certain community of [#permalink]

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14 May 2015, 10:07
E. Mean and median aren't interchangeable. The mean can have a very different value from the median if there are many households with very high or low incomes. Without the value of the mean provided, there's no way to predict what it will be.
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12 Jun 2016, 03:46
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Re: The median annual household income in a certain community of   [#permalink] 12 Jun 2016, 03:46
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