








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

Thread Tools  Search this Thread  Display Modes 
#1




Biostatistics #16  Conclusions from this study
In a random sample of 500 school children in Baltimore, 27% are found to be susceptible to measles. The standard error of the percentage susceptible is 2%. From this it is correct to conclude that?
a. The probability is 95% that the percentage susceptible for all schoolchildren in Baltimore is between 25% and 29%. b. The sample is biased. c. Twentyfive of the children in the random sample were misclassified. d. The data should be age adjusted. e. The probability is 95% that the percentage susceptible for all schoolchildren in Baltimore is between 23% and 31%. 
The above post was thanked by:  
#4




correct answer
Quote:
Why not a)? because, a 95% CI follows this formula: "parameter" + or [ Z_score x SE ] In this case: parameter = 27% SE = 2% Z_score = 1.96 (aprox. 2) 95% CI = 27 + or  [ 2 x 2 ] = [ 23, 31] 
The above post was thanked by:  
rulz (10062011) 
#5




standard error of the percentage susceptible is 2%."""
the concept that i understand is that there is skepticism about the true place of the mean that oscillates in a + 2% range!!! we have statistical certainty (which is only 95% from the utopian 100percent certainty) that this (percentage of susceptible children) will belong to the world of Mean+SEM ... Please correct me bebix 
#6




Quote:
When we are talking about X%CI, the only thing that we are saying is: We are 95% confident (or there is a 95% certainty) that the interval contains the "true" parameter (e.g. population mean) We are 95% confident that the true parameter is between [lower bound] and [upper bound] and the classic formula is mean (or proportion, OR, RR...) plus or minus the product of the Z_score (type I error = 5% = Z_score two sided of 1.96  2.5% lower tail and 2.5% upper tail) times the SE Please check this other post: Systolic blood pressure and confidence interval 
Tags 
BiostatisticsEpidemiology, Step1Questions 
Thread Tools  Search this Thread 
Display Modes  

Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Biostatistics #8  Type of study 2  bebix  USMLE Step 1 Forum  12  11242013 09:22 PM 
Biostatistics #11  Type of study (4 question)  bebix  USMLE Step 1 Forum  14  06152011 01:15 AM 
Biostatistics #6  Type of study  bebix  USMLE Step 1 Forum  9  06032011 06:19 AM 
How do I improve my Biostatistics?  Doctor Queen  USMLE Step 1 Forum  2  10172010 09:43 PM 
