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#1
08-01-2013
 USMLE Forums Master Steps History: 1+CK+CS+3 Posts: 1,353 Threads: 94 Thanked 877 Times in 507 Posts Reputation: 890
Statistics question

Study is made to analyze the relationship of vitamin B12 and methylmalonyl-COA level. Researchers show that there is an inverse relationship, the correlation coefficient is -0.7 (p<0.05). How much variability in plasma methylmalonyl-COA is explained by B12 intake?

A) >0.95
B) 0.70
C) <0.05
D) 0.49
E) 0.25
F) 99.7
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 The above post was thanked by: mycoplasma (08-01-2013), rg99 (08-02-2013)

#2
08-01-2013
 USMLE Forums Addict Steps History: Not yet Posts: 120 Threads: 21 Thanked 36 Times in 30 Posts Reputation: 46

D.49
whats the ans?
 The above post was thanked by: DocSikorski (08-02-2013)
#3
08-01-2013
 USMLE Forums Veteran Steps History: Not yet Posts: 205 Threads: 58 Thanked 19 Times in 16 Posts Reputation: 29

B as I guess, but really dont know how to calculate variability ???
need to explain , if that is possible

#4
08-01-2013
 USMLE Forums Master Steps History: 1+CK+CS Posts: 1,039 Threads: 189 Thanked 570 Times in 323 Posts Reputation: 580

A) >0.95 because p is <0.05
#5
08-02-2013
 USMLE Forums Master Steps History: 1+CK+CS+3 Posts: 1,353 Threads: 94 Thanked 877 Times in 507 Posts Reputation: 890

rg99 got it right

You take the square of correlation coefficient to predict variability
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Ambition is a dream with a V8 engine. EP
 The above post was thanked by: rg99 (08-02-2013)
#6
08-02-2013
 USMLE Forums Addict Steps History: Not yet Posts: 120 Threads: 21 Thanked 36 Times in 30 Posts Reputation: 46

whats the right ans??
#7
08-02-2013
 USMLE Forums Newbie Steps History: Step 1 Only Posts: 1 Threads: 0 Thanked 0 Times in 0 Posts Reputation: 10

A? The study is statistically significant and meaning there is less than 0.05 probability that it was due to chance alone. Reverse this statement: there is >0.95 probability that the variability is explained by the exposure
#8
08-03-2013
 USMLE Forums Master Steps History: 1+CK+CS+3 Posts: 1,353 Threads: 94 Thanked 877 Times in 507 Posts Reputation: 890

Guys are you kidding me? Im sayin:

"rg99 got it right"

Which means 0.49 is the snswer
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Ambition is a dream with a V8 engine. EP
#9
08-30-2013
 USMLE Forums Scout Steps History: Not yet Posts: 41 Threads: 9 Thanked 9 Times in 8 Posts Reputation: 19
??

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kill the MLE.....
#10
08-30-2013
 USMLE Forums Master Steps History: Step 1 Only Posts: 567 Threads: 25 Thanked 524 Times in 263 Posts Reputation: 534

Quote:
 Originally Posted by usmlestep1taker Can somebody explain the answer to this question! Please.
To calculate the variability Doc is explaning that you just take it to the SQUARE 7x7 = .49

nice.
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 Tags Biostatistics-Epidemiology, Step-2-Questions

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