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#1
03-13-2013
 USMLE Forums Guru Steps History: 1+CK+CS Posts: 333 Threads: 162 Thanked 284 Times in 147 Posts Reputation: 294
Mean, Median, Mode

As a part of a study to determine factors influencing mortality in an intensive care unit, serum creatinine concentrations (in mg/dL) are obtained from 10 consecutive patients at the time of admission to the intensive care unit. The results are shown in the graph. Which of the following statements regarding the sizes of the mean, median, and mode of the serum creatinine values is correct?

A. The mean is larger than the median
B. The median is larger than the mean
C. The median is larger than the mode
D. The mode is larger than the median
E. The mean, median, and mode cannot be determined because the distribution is not normal (gaussian)

click image to enlarge

#2
03-13-2013
 USMLE Forums Veteran Steps History: 1+CK+CS Posts: 214 Threads: 29 Thanked 62 Times in 40 Posts Reputation: 72

A is my answer.

correct me if im wrong.
the 10 values are - 0.5 0.5 0.5 1 1 1 1 2 4 5

mean - 8.3
MOde (MOst number) - 1
MEDian (MIDdle number) - in this case 1+1/2 = 1.
#3
03-13-2013
 USMLE Forums Veteran Steps History: 1+CK+CS Posts: 259 Threads: 8 Thanked 115 Times in 78 Posts Reputation: 125

Negative skew it looks like

SO the answer is C. Median > mode.

MAY BE WRONG

Last edited by mdsoon; 03-13-2013 at 01:32 PM.

#4
03-13-2013
 USMLE Forums Guru Steps History: Not yet Posts: 375 Threads: 17 Thanked 131 Times in 81 Posts Reputation: 147

Quote:
 Originally Posted by mdsoon Negative skew it looks like SO the answer is C. Median > mode. MAY BE WRONG
If it is negative skewd , isn't it gonna be Mode > median > mean???

While positive skewed will be Mean > Median > mode ???

So if thats the case , the answer should be D.
#5
03-13-2013
 USMLE Forums Veteran Steps History: 1+CK+CS Posts: 214 Threads: 29 Thanked 62 Times in 40 Posts Reputation: 72

if it is positive skew option A and D are correct.
if it is negative skew option B and D are correct.

yes/no?
#6
03-13-2013
 USMLE Forums Veteran Steps History: 1+CK+CS Posts: 259 Threads: 8 Thanked 115 Times in 78 Posts Reputation: 125

now 'im even more confused

so whats the right answer?
#7
03-13-2013
 USMLE Forums Veteran Steps History: 1+CK+CS Posts: 214 Threads: 29 Thanked 62 Times in 40 Posts Reputation: 72

i think its A based on my calculation. but i dont know if thats the right method to use.
#8
03-13-2013
 USMLE Forums Guru Steps History: 1+CK+CS Posts: 333 Threads: 162 Thanked 284 Times in 147 Posts Reputation: 294
PLZ help

I don't know the answer. I think A might be correct, but some believe that B might be correct. This is a NBME Q. http://www.usmleforum.com/files/forum/2009/1/444772.php
#9
03-13-2013
 USMLE Forums Veteran Steps History: 1+CK+CS Posts: 259 Threads: 8 Thanked 115 Times in 78 Posts Reputation: 125

that post was made in 2005 and still nobody knows the answer.. LOST CAUSE MAYBE..

take it as a WFT question and move on.
 The above post was thanked by: Doc4Step1 (03-13-2013), Evergreen (03-13-2013)
#10
03-13-2013
 USMLE Forums Veteran Steps History: Step 1 Only Posts: 283 Threads: 35 Thanked 206 Times in 115 Posts Reputation: 216

Quote:
 Originally Posted by Evergreen As a part of a study to determine factors influencing mortality in an intensive care unit, serum creatinine concentrations (in mg/dL) are obtained from 10 consecutive patients at the time of admission to the intensive care unit. The results are shown in the graph. Which of the following statements regarding the sizes of the mean, median, and mode of the serum creatinine values is correct? A. The mean is larger than the median B. The median is larger than the mean C. The median is larger than the mode D. The mode is larger than the median E. The mean, median, and mode cannot be determined because the distribution is not normal (gaussian) Attachment 3079 click image to enlarge Please explain the answer...
This is negative skewed. General: Mode > Median > Mean. Specific: Median > Mean. And this is what they look for - Specific. Therefore, the answer shall be B.
 The above post was thanked by: succinylcholine (03-13-2013)
#11
03-13-2013
 USMLE Forums Addict Steps History: CK Only Posts: 125 Threads: 24 Thanked 30 Times in 21 Posts Reputation: 40

THE ANSWER IS B, because negatively skewed plots the median is greater than the mean
#12
03-13-2013
 USMLE Forums Veteran Steps History: CS Only Posts: 219 Threads: 44 Thanked 44 Times in 33 Posts Reputation: 54

Quote:
 Originally Posted by samren17 if it is positive skew option A and D are correct. if it is negative skew option B and D are correct. yes/no?
I agree!
Which makes me think maybe the last choice us correct?
So i looked up whats Gaussian distribution, only found out that its the normal distribution, which contradicts whats mentioned in that last choice =s

http://hyperphysics.phy-astr.gsu.edu/%E2%80%8Chbase/math/gaufcn.html#c2

http://www.thefreedictionary.com/_/dict.aspx?word=Gaussian+distribution
#13
03-13-2013
 USMLE Forums Veteran Steps History: 1+CK+CS Posts: 214 Threads: 29 Thanked 62 Times in 40 Posts Reputation: 72

@doctor ali - what is the "specific: - is it a medical term used in these graph situations or something else?

@faith - well your work of looking it up paid off as something right.im done for today.see you guys tomoro.
#14
03-13-2013
 USMLE Forums Addict Steps History: Not yet Posts: 135 Threads: 3 Thanked 73 Times in 48 Posts Reputation: 83

A. The mean is larger than the median

I believe that's the right answer. The plot/graph given is not a frequency plot; I mean the y-axis is not the frequency of ppl who have a certain creatinine value, it's the actual raw value of their creatinine level. We simply add up the values and divide by 10 (total number of ppl/values to get the mean), and of course the median is the value in the middle in ascending order.

If instead of having creatinine concentration on the y-axis, we had number of ppl (frequency), and we had on the x-axis creatinine values. Then this graph would be negatively skewed, and mode>median>mean could apply.
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Last edited by slowpoke; 03-13-2013 at 09:47 PM.
#15
03-14-2013
 USMLE Forums Newbie Steps History: Not yet Posts: 1 Threads: 0 Thanked 0 Times in 0 Posts Reputation: 10

Quote:
 Originally Posted by Evergreen As a part of a study to determine factors influencing mortality in an intensive care unit, serum creatinine concentrations (in mg/dL) are obtained from 10 consecutive patients at the time of admission to the intensive care unit. The results are shown in the graph. Which of the following statements regarding the sizes of the mean, median, and mode of the serum creatinine values is correct? A. The mean is larger than the median B. The median is larger than the mean C. The median is larger than the mode D. The mode is larger than the median E. The mean, median, and mode cannot be determined because the distribution is not normal (gaussian) Attachment 3079 click image to enlarge Please explain the answer...
is their any one who can tell the right ans even i m thinking for a

#16
03-14-2013
 USMLE Forums Veteran Steps History: Step 1 Only Posts: 283 Threads: 35 Thanked 206 Times in 115 Posts Reputation: 216

Quote:
 Originally Posted by samren17 @doctor ali - what is the "specific: - is it a medical term used in these graph situations or something else? @faith - well your work of looking it up paid off as something right.im done for today.see you guys tomoro.

I mean general speaking vs. specific speaking.

In negative skewed:
General speaking: Mode > Median > Mean
Specific speaking: Median > Mean

In positive skewed:
General speaking: Mean > Median > Mode
Specific speaking: Mean > Median

In most cases, they want specific speaking answers.

 Tags Biostatistics-Epidemiology, Figures-, Step-1-Questions

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