Identify the type of problem most likely to occur with each of the sampling or experiment methods below: Placebo effect Nonresponse Undercoverage Response bias a) A particular group or groups are left out when collecting a sample from a population. b) A treatment is administered to all members of sample, and the results are observed and measured. c) A sample of people is randomly constructed from a government database and each sample member is mailed a survey and asked to complete and return it. d) A sample of people are contacted by phone and asked about if they have ever performed some illegal activity and if so how frequently.