§ 53.13 – Why do such annual fluctuations in sample data require a margin of safety?

(a)    FTA’s 95% confidence and 10% precision levels are imposed on your estimates of annual service-consumed data.

(b)   The template, on the other hand, can only impose these requirements on your template sampling plans, but not on the estimates you develop with data collected according to your template sampling plans.

(c)    Whether the estimates of annual service-consumed data from the sample data collected according to the template sampling plans meet FTA’s requirements depends on how the sample data fluctuate over time:

(1)   If the statistical variation is greater in the sample data used to develop your template sampling plan, your estimates will meet FTA’s requirements.

(2)   If the statistical variation is smaller in the sample data used to develop your template sampling plan, your estimates may not meet FTA’s requirements.  The margin of safety is built in to prevent such violations from happening.