Confidence Interval

Oct 2019
33
1
united states
Suppose that insurance companies did a survey. They randomly surveyed 400 drivers and found that 340 claimed they always buckle up. We are interested in the population proportion of drivers who claim they always buckle up.


Construct a 95% confidence interval for the population proportion who claim they always buckle up.
(i) State the confidence interval. (Round your answers to four decimal places.)

I used the calculator z interval and give .8483, .8518. I dont know how find the mean? . I dont know.
 

Debsta

MHF Helper
Oct 2009
1,313
600
Brisbane
You don' t want to find the mean, you want to find the proportion. You are asked to find the 95% CI for the population PROPORTION, not the mean.
 
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Oct 2019
33
1
united states
Yes but I don't know the mean x to use in the calculator. Using z interval