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Thanks Ganesh! Could you please explain why you multiply 5400 by 7? I understand this is a number of all values for x from 13 to 19, but I don't get why you add it to the formula. thanks

Re: IR - Graphical Interpretation Sample Question [#permalink]
10 Mar 2013, 07:25

Hi,

The equation is y=525x -5400

for x=13 it becomes y= 525 ( 13) -5400 for x= 14 it becomes y= 525 ( 14)- 5400 for x= 15 it will be y= 525 ( 15) -5400 Similarly continuing till x=19 and we will have 525 ( 19) - 5400

Since we have to find the sum ,when we add all these up there will a total of 7 expressions and each of them will have the term 5400

So we could take 525 as a common factor and we will have 5400 seven times which can be expressed as 525 ( 13+14+15+...19) - (5700 *7)

Re: IR - Graphical Interpretation Sample Question [#permalink]
10 Mar 2013, 20:03

Rock750 wrote:

Hi,

if you give the graph a closer look, you will see that :

Between 12 and 21, there are 10 values

And between 21 and 30, there are 10 values [The set of ages is an evenly spaced set i.e the average equals the median, which is equal to 21]

So, you can pick 1 value from the former and 1 value from the latter and average the corresponding two values of mass.

For point B (16, 3000) and another point let's call it D ( 25, 5500) , the average mass is : (3000 + 5500)/2= 4250, which is between 4000 and 5000..

This holds true for any values selected from the previous intervals because the graph is incremental

Hope that helps !

This is what I did in the first place, but I picked A (12, 900) and D (25, 5500) and came up with the average mass of 3200 (900+5500)/2. why didn't it work? thanks

Re: IR - Graphical Interpretation Sample Question [#permalink]
11 Mar 2013, 01:03

LinaNY wrote:

This is what I did in the first place, but I picked A (12, 900) and D (25, 5500) and came up with the average mass of 3200 (900+5500)/2. why didn't it work? thanks

Hi LinaNY, You should take B from the former , it's more representative than any other value picked from the first intervall because it seems to be the middle point i.e the average of the first intervall while for the latter, it seems to have a constant corresponding mass of almost all the values picked from 21 to 30 --> 5500 . I know it's tricky but when it's about IR, always try to pick the easiest values i.e the most logical ones. Hope that helps ! _________________

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Re: IR - Graphical Interpretation Sample Question [#permalink]
06 May 2013, 07:49

Just by looking at the graph you can see that weights > 5000 account for 1/3 of the age range. With the Median weight at age 16 being 3000 lbs, you can see that the mean will be much higher than 3000 lbs.