Biostatistics #2 - what test should I use? - USMLE Forums
USMLE Forums Logo
USMLE Forums         Your Reliable USMLE Online Community     Members     Posts
Home
USMLE Articles
USMLE News
USMLE Polls
USMLE Books
USMLE Apps
Go Back   USMLE Forums > USMLE Step 1 Forum

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


Reply
 
Thread Tools Search this Thread Display Modes
  #1  
Old 06-01-2011
bebix's Avatar
USMLE Forums Master
 
Steps History: 1+CK+CS+3
Posts: 1,357
Threads: 194
Thanked 3,268 Times in 881 Posts
Reputation: 3278
Stats Biostatistics #2 - what test should I use?

A new drug for the treatment of malaria was tested against chroloquine sulphate. The results were as follows:

malaria.bmp

To test the effectiveness of the new drug in the management of malaria, we carry out:

a. Paired T-test
b. Z-test for two proportions
c. T-test for two proportions
d. T-test for two independent means
Reply With Quote Quick reply to this message



  #2  
Old 06-01-2011
USMLE Forums Guru
 
Steps History: Not yet
Posts: 324
Threads: 70
Thanked 238 Times in 144 Posts
Reputation: 248
Default

Paired T test.
Reply With Quote Quick reply to this message
The above post was thanked by:
bebix (06-01-2011)
  #3  
Old 06-02-2011
Claus_CU's Avatar
USMLE Forums Addict
 
Steps History: 1 + CS
Posts: 113
Threads: 8
Thanked 89 Times in 61 Posts
Reputation: 99
Default

My answer is B) Z-test for two proportions
Reply With Quote Quick reply to this message
The above post was thanked by:
bebix (06-02-2011)
 
  #4  
Old 06-02-2011
USMLE Forums Guru
 
Steps History: Not yet
Posts: 339
Threads: 94
Thanked 331 Times in 150 Posts
Reputation: 291
Default

is it paired t-test??
Reply With Quote Quick reply to this message
The above post was thanked by:
bebix (06-02-2011)
  #5  
Old 06-02-2011
bebix's Avatar
USMLE Forums Master
 
Steps History: 1+CK+CS+3
Posts: 1,357
Threads: 194
Thanked 3,268 Times in 881 Posts
Reputation: 3278
Wink

somebody else???
Reply With Quote Quick reply to this message
  #6  
Old 06-02-2011
Dr_Laura's Avatar
USMLE Forums Guru
 
Steps History: 1+CK+CS
Posts: 499
Threads: 85
Thanked 529 Times in 222 Posts
Reputation: 539
Default

T test for independent means because it's 2 different meds????
__________________
YouTube:
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Facebook:
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Reply With Quote Quick reply to this message
The above post was thanked by:
bebix (06-02-2011)
  #7  
Old 06-02-2011
Banned
 
Steps History: 1 + CK
Posts: 751
Threads: 133
Thanked 308 Times in 192 Posts
Reputation: 318
Default

The answer is B. This is clearly a randomized control trial. In RCTs, you calculate RRs (which is a proportion if you think of it). Now, depending on whether the outcome is continuous, binary (like case-control studies), time-to-event (like cohort studies or RCTs), we use different tests to come up with a P-value to determine whether there is a statistically significant difference between the 2 groups. In this case, no means are involved, so it eliminates the use of T-tests, whether paired or not.
Hope this helps
Wow, the step 1 forum is bombarded with questions...it's pretty crowded. Lol.
Reply With Quote Quick reply to this message
  #8  
Old 06-02-2011
bebix's Avatar
USMLE Forums Master
 
Steps History: 1+CK+CS+3
Posts: 1,357
Threads: 194
Thanked 3,268 Times in 881 Posts
Reputation: 3278
Correct Answer correct answer

B. Z-test for two proportions

So, here we have:

- The proportion of cured subjects with Chroloquine = 129/184
- The proportion of cured subjects with New Drug = 80/103


Then, we could use:
1.- Z-test for two proportions
2.- Chi-squared / Fisher's exact test


Basic rule of thumb

Are two proportions different? Chi-squared / Z-test for two proportions;
Are two means different? t-test;
Are more than two means different? ANOVA or “F-test”

Ref:
Statistical Methods for Rates & Proportions
by Joseph L. Fleiss, Bruce Levin, Myunghee Cho Paik
Reply With Quote Quick reply to this message
The above post was thanked by:
docoftheworld (06-05-2011), erickven (05-21-2016), rulz (10-06-2011), singapur_md (06-02-2011)



Reply

Tags
Biostatistics-Epidemiology, Step-1-Questions

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the USMLE Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:
Medical School
Choose "---" if you don't want to tell. AMG for US & Canadian medical schools. IMG for all other medical schools.
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.

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.



Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes


Similar Threads
Thread Thread Starter Forum Replies Last Post
Biostatistics #3 - Screening test bebix USMLE Step 1 Forum 9 06-06-2011 02:17 PM
How do I improve my Biostatistics? Doctor Queen USMLE Step 1 Forum 2 10-17-2010 09:43 PM
Biostatistics Section of First Aid mpz013 USMLE Step 1 Forum 1 10-05-2010 08:03 PM
Let's Discuss Biostatistics raheel_memon USMLE Step 1 Forum 4 09-01-2010 06:27 AM

RSS Feed
Find Us on Facebook
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.

USMLE® & other trade marks belong to their respective owners, read full disclaimer
USMLE Forums created under Creative Commons 3.0 License. (2009-2014)