Measuring Usability Homepage
Quantitative Usability, Statistics & Six Sigma by Jeff Sauro



April 14, 2008 | asked by Jeff Phillips :

Question : If 350 respondents out of a random sample of 1,000 Americans reported that they did not trust their government, what is your estimation at a 99% confidence level of the proportion of the American population who do not trust their government?

Answer :

Calculate a confidence interval around the proportion .35 (350/1000) using the confidence interval around a proportion calculator and change the confidence level to 99%. While I recommend using the Adjusted Wald, because this sample size is large enough, there is little difference between the standard Wald formula and Adjusted Wald.

The Adj. Wald formula shows that with this sample (assuming it is representative of the population we're interested in)  we can be 99% confident between 31.2% and 38.9% of the total American population do not trust their government.

See also question question 160 which is almost identical to this one.


How helpful was this answer?
Avg. Rating: 0 ( 0 )
Question Tags

Tag Name # Vote
Adjusted Wald2
Confidence Intervals2

New Tag:   



User Provided Answers & Comments :
No user comments or answers posted yet.


Comment or Update Answer:
Name
Email Address Not Published