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 USMLE Step 1 Forum USMLE Step 1 Discussion Forum: Let's talk about anything related to USMLE Step 1 exam

#1
11-03-2012
 USMLE Forums Addict Steps History: 1+CK+CS Posts: 106 Threads: 35 Thanked 17 Times in 10 Posts Reputation: 27
Biostat

Serum LDL conc are measured in blood sample collected from 100 healthy volunteers. The data follow normal distribution. The mean and standard deviation for this group is 130 mg/dl and 20mg/dl. Standard error of mean is 5.0. 95 % confidence interval about mean is 120 - 140 mg/dl. If blood samples are collected from 25 volunteers instead of 100, which of the following best expressed the expected impact on standard error and 95% confidence interval about the mean ?
Standard error Width of 95% CI
A. de de
B. de in
C de no change
D in de
E in in
F in no change
G no change de
H no change in
I no change no change

#2
11-03-2012
 USMLE Forums Master Steps History: 1+CK+CS+3 Posts: 1,186 Threads: 119 Thanked 822 Times in 434 Posts Reputation: 832

i think it's E..........increase increase

if sample size decrease------standard error increase which eventually increase 95% CI .

thanks
#3
11-03-2012
 USMLE Forums Master Steps History: 1+CK+CS Posts: 1,039 Threads: 189 Thanked 570 Times in 323 Posts Reputation: 580

E in in

Message:
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