Cal. Code Regs. tit. 25, § 6060
(b) The files and records of displaced persons and property owners should be selected at random. The review should include any cases that were identified by previous monitoring as requiring corrective action and should assess the public entity's progress in taking corrective action. Both relocation and acquisition activities should be covered by the review.
(c) After the records and files have been reviewed, the reviewer should select cases for further evaluation through personal interviews with displaced persons and/or owners and the inspection of housing to which persons have moved. The interviews and housing inspections should serve both to spot check the accuracy of the information obtained in the examination of the records and files and give the reviewer a better perspective on the agency's performance.
The number and type of cases for which interviews and housing inspections are to be carried out should reflect the reviewer's judgment based on the information he has just reviewed. Generally, an interview and inspection should be carried out for at least one of every five cases for which the files and records have been reviewed. Only where the number of persons displaced is less than 25 should the number of interviews and inspections be less than 10. In no case should the number of interviews and inspections be lower than the lesser of five and the number of persons displaced. To the extent possible, the interviews should cover a representative cross section of the types of cases in the agency's workload: e.g., relocation cases involving families of various sizes as well as individuals and business concerns (including both owners and tenants), and acquisition transactions involving residential, commercial and industrial properties.
(d) In addition to the above, the following factors are among those which should be considered: