10 C.F.R. § 429.54
(a) Sampling plan for selection of units for testing.
(2) For each basic model of metal halide lamp ballast selected for testing, a sample of sufficient size, not less than four, shall be selected at random and tested to ensure that:
(i) Any represented value of estimated energy efficiency calculated as the measured output power to the lamp divided by the measured input power to the ballast (Pout/Pin), of a basic model is less than or equal to the lower of:
(A) The mean of the sample, where:

Or,
(B) The lower 99-percent confidence limit (LCL) of the true mean divided by 0.99.

And x is the sample mean; s is the sample standard deviation; n is the number of samples; and t0.99 is the t statistic for a 99% two-tailed confidence interval with n-1 degrees of freedom (from appendix A).
(b) Certification reports.
[76 FR 12451, Mar. 7, 2011; 76 FR 24780, May 2, 2011; 76 FR 46202, Aug. 2, 2011]