1. When you are given a list of raw data you should round the mean and standard deviation to 1 more decimal place than what the data has. If your data has no decimals you round to 1 decimal place.If your data has 1 decimal place you round to 2 decimal places. If your data has 2 decimal places you round to 3 decimal places. If your data has 3 decimal places you round to 4 decimal places. 2. When calculating confidence intervals for the mean (using z or t), round your margin of error ( E ) to match the number of decimal places in the standard deviation. 3. When calculating confidence intervals for the proportion ( z ), round your margin of error ( E ) and the sample proportion (p hat) to 3 decimal places. 4. When calculating confidence intervals for the standard deviation or variance ( X^{2} ), round your margin of error ( E ) to match the number of decimal places in the standard deviation.
