## Sample Size for Measuring Rates

Another kind of variable of interest is a rate. Measuring rates may not be feasible or very meaningful at a local level, but they certainly mean a lot at a higher level (larger geographic area/population.

Some examples of rates that are oftne studied and followed by development agencies are:

1. Infant Mortality Rate (IMR)

2. Maternal Mortality Rate (MMR)

3. Many low prevalence variables/indicators where proportion may not be applicable, but instead a per thousand, per hundred thousand or per million is more appropriate

For measuring such rates, refer to the formulae below:

Some examples of rates that are oftne studied and followed by development agencies are:

1. Infant Mortality Rate (IMR)

2. Maternal Mortality Rate (MMR)

3. Many low prevalence variables/indicators where proportion may not be applicable, but instead a per thousand, per hundred thousand or per million is more appropriate

For measuring such rates, refer to the formulae below:

**Single Rate - Absolute Precision Method**

Single Rate - Power Method

Single Rate - Power Method

It is one thing to measure a single rate, and it is another thing to compare two rates. It is not really a right or recommended way to use the sample size calculation for single rate and apply it to two groups separately and then compare the results. Hence, for comparing two rates, refer to the formulae below:

**Compare Two Rates - Power Method**

**Compare Two Rates - Precision Method**

**Compare Two Rates - Power Calculation**

**Compare Two Rates - Detectable Difference**