NBME Form 3/ Block 3/ Q 49 - squidward

[ArchivalUser]

Could anyone please give a proper explanation for this question. I searched everywhere where half the people picked A and half picked B. The given answer is B. Any help would be greatly appreciated. Thanks in advance.


Note: Please look at the graph/figure in the nbme as I couldn't copy and paste that here.

49. 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)

[ArchivalUser]

Squidward, this is the way I understand the Q.
From the graph, if you calculate the mean Cr value it is 3.3
But when you see the median, it is 1.5. Therefore the graph is positivly skewed which means the mean is greater than the median. So the Ans is :
A
Don't you think?

[ArchivalUser]

bigtime99, that does makes sense to me. Thanks.

it's just that some ppl had weird explanations and were spinning my head.

[ArchivalUser]

Let me try and correct me if wrong, first let get the MEDIAN.

we have 10 patients, to find the median, you need to put the values in order, then find the middle value: in this case the number are already in increasing order.
If there are two values in the middle then you find the mean of these two values, so if you look at the graph we have 5 and 6 in the middle and their value is 1.

Median=(1.0+1.0)/2=1.0

Then, To find the mean, you need to add up all the data, and then divide this total by the number of values in the data.

if you look at the graph, it is obvious that the mean is greater than 1.0, you can check by adding all creatinine and dividing by 10(waste of time)

So the answer is

A. The mean is larger than the median


Best luck.
OKT3.

[ArchivalUser]

bigtime99,

how did you get the median as 1.5. Shouldn't it be 3 instead when looking at the Cr values (0.0 to 0.5)

[ArchivalUser]

squidward
how did u get median=3, please detailed explanations !!!!!!!

[ArchivalUser]

ok thanks OKT3,

I got the median part. Having trouble with the mean. My understanding was, in order to find the mean, it's summation of all numbers from 1 to 10 and then divide that by 10.

But, in this case, we add all the creatinine values (0.0 to 5.5) and divide that by 10 .....

[ArchivalUser]

oh, i was lookin at the Y axis (creatinine) 0 to 5.5 when I got the median

3 has five numbers below it and five above


but i guess ur explanation makes more sense

[ArchivalUser]

okt3, i was wayyyyyyyy off the chart for this one . Ignore how I got the Median. You are right.


I just wanna make sure that in order to get the mean, we need to add all the creatinine values given along the Y axis and then divide by 10 ???? which is obviously greater than 1. (but I'm just asking)


thanks in advance and appreciate the great explanation above.

[ArchivalUser]

LET calculate mean based on creat value from all patient if you want to:

Pt 1=0.5
pt2=0.6
pt3=0.7
pt4=0.8
pt5=1.0
pt6=1.0
pt7=1.1
pt8=2.0
pt9=4.0
pt10=5.0

0.5+0.6+0.7+0.8+1.0+1.0+2.0+4.0+5.0=15.6

mean=15.6/10=1.56