The National Health Survey uses household interviews to describe the health- related habits of U.S. adults. From these interviews they estimate population parameters associated with behaviors such as alcohol consumption, cigarette smoking, and hours of sleep for all U.S. adults. In the 2005-2007 report, they estimated that 30% of all current smokers started smoking before the age of 16. Imagine that we want to verify this estimate. So we randomly select a sample of 100 smokers and calculate the proportion who started smoking before the age of 16. How much error do we expect in the sample proportions if the 30% is correct for the population overall? Use the applet and a give an error based on 2 standard deviations. 

Here's the applet for the simulation: 

p = 0.3 

n = 100 

Show Standard Deviation Bars 

Run Simulation (5000 Samples) 

Actual Sample proportion (p̂):        0.5 

Sampling Distribution: mean = 0.5009 standard deviation = 0.0458.