### Rounding Rules for Confidence Intervals

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 ( X2 ), round your margin of error ( E ) to match the number of decimal places in the standard deviation.

5. When finding the sample size round n to the next larger whole number.

 Type of information Rounding rules Raw data One additional decimal place beyond  your data. Margin of Error ( E ) Match the number of decimal places in the standard deviation. Proportions ALWAYS round to three decimal places.