of confidence interval) is to be maintained. B. For a given level of confidence, sample size and standard deviation, the width of a confidence interval for the mean will be the same regardless of whether the standard deviation is a population or sample measure. C. Where no prior information is available concerning an estimate of the true population proportion, a conservative estimate of the sample size required to obtain a confidence interval with given levels of confidence and precision can be determined by letting the proportion equal 1/2. O only A is true O only A and B are true O only A and C are true O only B and C are true O A, B and C are true