Skip lot sampling and inspection are special procedures for inspecting stationary lots in which only one-half or one-fourth of the lots offered for inspection are formally inspected. Skip lot sampling and inspection procedures may be instituted only when all of the following conditions are met:

(a) When authorized by the Administrator and acceptable to the user and producer, if different from the user.

(b) When inspection is origin inspection (see § 42.102).

(c) When all lots can be expected to be of essentially the same quality.

(d) When lots from the producer are currently on, or eligible to be on, either normal or reduced inspection.

(a) Following skip lot procedure authorization, inspect every lot consecutively offered for inspection using normal inspection procedures as set forth in Subpart B of this part. When 10 consecutive lots are acceptable, inspect only one-half of the lots offered for inspection using normal inspection procedures. While on the one-half inspection rate, when 10 consecutively inspected lots are acceptable, inspect only one-fourth of the lots offered for inspection using normal inspection procedures. While on the one-half or one-fourth inspection rate, if any formally inspected lot is unacceptable, revert immediately to the inspection of every lot using normal inspection procedures and recommence the above procedure. See § 42.123 for a flow diagram of the skip lot sampling plan.

(b) Two exceptions to the procedures in paragraph (a) of this section are as follows:

(1) The skip lot sampling and inspection rate of one-half can be instituted immediately if the lots from the producer are currently on, or eligible to be on, reduced inspection and all other conditions in § 42.120 are met. After skip lot sampling and inspection begins, however, only normal inspection is permitted.

(2) While inspecting every lot consecutively as offered for inspection, i.e., while not on the one-half or one-fourth sampling and inspection rate, if requirements for switching from normal to tightened inspection are met as specified in § 42.108 then skip lot procedures terminate, tightened inspection is initiated, and stationary lot sampling and inspection procedures in Subpart B are instituted. Skip lot procedures may be instituted again only when all conditions of § 42.120 are met.

(c) All lot selections for the one-half and one-fourth inspection rates must be strictly random (for example, not every other lot or every fourth lot). Use of random number tables, coin flipping, or numbered cards is encouraged.

(d) Preliminary scanning procedures (see § 42.105) shall be used on all lots scheduled for formal inspection and also shall be used on lots not scheduled for inspection (“skipped” lots) whenever the inspector feels such action is prudent to further insure the acceptability of such lots.

Whenever appropriate, the procedures for classifying and recording defects in § 42.106 and for appeal inspections in § 42.108 also apply to skip lot sampling and inspection.