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#1
06-01-2011
 USMLE Forums Master Steps History: 1+CK+CS+3 Posts: 1,357 Threads: 194 Thanked 3,259 Times in 881 Posts Reputation: 3269
Biostatistics #1 - triglyceride levels and degree of atherosclerosis

An investigator determines the correlation coefficient between triglyceride levels and degree of atherosclerosis in sampled blood vessels to be +1.67. On the basis of this you would conclude that:

A. Triglyceride level is a good predictor of atherosclerosis
B. Triglyceride level is not a good predictor of atherosclerosis
C. High triglyceride levels cause atherosclerosis
D. Atherosclerosis causes high triglyceride levels
E. The investigator has incorrectly determined the correlation coefficient.

Last edited by bebix; 06-01-2011 at 06:42 PM.
 The above post was thanked by: Claus_CU (06-02-2011), mle guy (06-02-2011), pass7 (06-02-2011), zaiody (06-01-2011)

#2
06-01-2011
 USMLE Forums Guru Steps History: Not yet Posts: 324 Threads: 70 Thanked 236 Times in 143 Posts Reputation: 246

positive relation as it is + and >1..
So i would go with A
 The above post was thanked by: bebix (06-01-2011)
#3
06-01-2011
 USMLE Forums Guru Steps History: 1+CK+CS+3 Posts: 406 Threads: 30 Thanked 140 Times in 108 Posts Reputation: 150

Quote:
 Originally Posted by struggle positive relation as it is + and >1.. So i would go with A

i think A too but y not C ??
 The above post was thanked by: bebix (06-01-2011)

#4
06-01-2011
 USMLE Forums Guru Steps History: Not yet Posts: 324 Threads: 70 Thanked 236 Times in 143 Posts Reputation: 246

Because its not the only factor causing atherosclerosis..
It shows a correlation (risk factor) but not a 100% causal factor..
I guess so..i dont know if i am wrong
#5
06-01-2011
 USMLE Forums Newbie Steps History: Not yet Posts: 9 Threads: 0 Thanked 5 Times in 5 Posts Reputation: 15

Maximum for correlation coefficien is +1. so I think E is correct!
 The above post was thanked by: bebix (06-01-2011)
#6
06-01-2011
 USMLE Forums Addict Steps History: 1+CK+CS Posts: 122 Threads: 6 Thanked 39 Times in 27 Posts Reputation: 49

E absuloutely ..
 The above post was thanked by: bebix (06-01-2011)
#7
06-01-2011
 USMLE Forums Scout Steps History: 1 + CS Posts: 33 Threads: 5 Thanked 17 Times in 9 Posts Reputation: 27

I think its E
b/c its more than 1
and the range usually b/t -1 to 1
and about choice C , it's absolutely wrong b/c the correlation coefficient is not a causal relation whenever you see causal relationship don't pick it in the exam
 The above post was thanked by: bebix (06-01-2011), mle guy (06-02-2011)
#8
06-02-2011
 USMLE Forums Addict Steps History: 1 + CS Posts: 113 Threads: 8 Thanked 88 Times in 61 Posts Reputation: 98

I think is E)
 The above post was thanked by: bebix (06-02-2011)
#9
06-02-2011
 USMLE Forums Master Steps History: 1+CK+CS+3 Posts: 1,357 Threads: 194 Thanked 3,259 Times in 881 Posts Reputation: 3269

The correlation coefficient (r) is an index of the extent to which two variable are linear associated. It can take the values BETWEEN +1.0 and -1.0, depending on the strenght of the LINEAR association and whether a positive change in x produces a positive or negative change in y. An r = 0 indicates the two variables are not linearly related.

click image to enlarge
 The above post was thanked by: docoftheworld (06-05-2011), mle guy (06-02-2011), pass7 (06-02-2011), struggle (06-02-2011)

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

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