# confidence interval of binomial disribution using standard deviation

Just as the normal distribution has the 68–95–99.7 rule with 68% of the data within +- 1 standard deviation and so on, does the binomial distribution too has something like that. Or does its being a discrete distribution, make it difficult to have a similar rule.

Actually, I wanted to calculate the number of trials required (binomial distribution case) for a given maximum error (+-0.1) and confidence level (95%) for different probabilities from 0:0.05:1 using the formula: max. error = standard error * no. of standard deviations for 95% confidence (as shown in http://en.wikipedia.org/wiki/Checking_whether_a_coin_is_fair: but instead of a normal approximation, i want to use the binomial distribution).

I would like to use the Clopper-Pearson (CP) interval, but the CP interval gives me the probability range, can I somehow use it to find the number of trials required when I fix the interval to +-0.1.

Any help is highly appreciated. Thanks.