95% Confidence Interval includes a zero! - USMLE Forums
 USMLE Forums         Your Reliable USMLE Online Community     Members     Posts
 Home USMLE Articles USMLE News USMLE Polls USMLE Books USMLE Apps
 USMLE Forums 95% Confidence Interval includes a zero!
 Register FAQs Members List Search Today's Posts Mark Forums Read

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

#1
01-21-2012
 USMLE Forums Newbie Steps History: Not yet Posts: 2 Threads: 1 Thanked 0 Times in 0 Posts Reputation: 10
95% Confidence Interval includes a zero!

Hi I have a question on biostatistics and hope to get some help. On page 55 of FA for step 1 2011, top right corner, it says: If the 95% CI for the mean difference between 2 variables includes 0, then there is no significant difference and H0 is not rejected. Why?

Sunny

#2
01-21-2012
 USMLE Forums Master Steps History: 1+CK+CS Posts: 851 Threads: 88 Thanked 710 Times in 380 Posts Reputation: 720

H0 is not rejected means H0 is accepted. means null hypothesis is true.i.e there is no difference between whatever we were measuring.

if comparing two means for eg

the height of the students in a class
group A -130 132 134 136 170cm
group B -120 125 134 138 165cm

now take a mean difference between above two groups by subtracting each value of group A from group B. calculate the 95%CI which is CI=from [mean-1.96(SEM)] to [mean+1.96(SEM)] which is the range of around 2 SD on both sides of mean right !
if the mean diff between the 2 groups has a zero somewhere that means there is no diff between them. i dont know how to calculate the CI of mean difference exactly but just understand the concept.
if mean difference between two groups have a zero then there is no difference.so H0 will not be rejected and null hypothesis will be true i.e the 2 groups are not very different from each other.

the above eg is just trying to explain you. it may not be accurate.
 The above post was thanked by: bunny (01-21-2012)
#3
01-21-2012
 USMLE Forums Newbie Steps History: Not yet Posts: 2 Threads: 1 Thanked 0 Times in 0 Posts Reputation: 10
Thank you.

I see. I understand the concept but somehow got confused by the wording. Thank you for explaining that to me.

 Tags Biostatistics-Epidemiology, First-Aid

Message:
Options

## Register Now

In order to be able to post messages on the USMLE Forums forums, you must first register.
User Name:
Medical School
Choose "---" if you don't want to tell. AMG for US & Canadian medical schools. IMG for all other medical schools.
 AMG IMG ---
USMLE Steps History
What steps finished! Example: 1+CK+CS+3 = Passed Step 1, Step 2 CK, Step 2 CS, and Step 3.

Choose "---" if you don't want to tell.

 Not yet Step 1 Only CK Only CS Only 1 + CK 1 + CS 1+CK+CS CK+CS 1+CK+CS+3 ---
Favorite USMLE Books
 What USMLE books you really think are useful. Leave blank if you don't want to tell.
Location
 Where you live. Leave blank if you don't want to tell.

## Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.