Posted by **nana** on Saturday, July 28, 2012 at 2:53pm.

According to a Harris Interactive poll conducted in 2009, 20% of American adults smoke. In a random sample of 500 American adults, what is the probability that no more than 100 smoke?

- statistics -
**MathGuru**, Saturday, July 28, 2012 at 7:16pm
Find mean and standard deviation.

mean = np = (500)(.20) = ?

standard deviation = √npq = √(500)(.20)(.80) = ?

Note: q = 1 - p

Once you have calculated the mean and standard deviation above, use z-scores to find the probability:

z = (x - mean)/sd

Use 100 for x.

After you find the z-score, check a z-table to determine your probability.

I hope this will help get you started.

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