Critics have written Schmidt's experiments in parapsychology have not been replicated.[7] Schmidt worked alone with no one checking his experiments. He was accused of being a careless experimenter.[8]
The psychologist C. E. M. Hansel found flaws in all of Schmidt's experiments into clairvoyance, precognition and psychokinesis. Hansel found that necessary precautions were not taken, there was no presence of an observer or second-experimenter in any of the experiments, no counterchecking of the records and no separate machines used for high and low score attempts. There were weaknesses in the design of the experiments that did not rule out the possibility of trickery. There was little control of the experimenter and unsatisfactory features of the machine employed.[2] Regarding the machine used in the experiments, Hansel wrote:
The most obvious weakness in Schmidt's machine is that the results are in no case recorded positively inside the machine. They are only revealed after processing data obtained from the resettable counters in the machine or from the paper punch connected it. While machines may be foolproof, human beings seldom are... If Schmidt had used two machines, his scores for high- and low-aiming runs could have been kept separate from the start. Nonresettable counters could have ensured that all attempts were recorded and some supervision of the use and recording of the counters would have instilled more confidence into readers of the reports than they are likely to have at present.[2]
The psychologists Leonard Zusne, Warren H. Jones supported Hansel and also noted:
The effect obtained by Schmidt and others is very small, at most a 2% deviation from the 50% chance level. Because of the very large number of trials that can be run with the REG in a short period of time (each trial lasts only a second or less), the odds against even such minuscule deviations range from 100 to 1 to several billions to 1. When, in addition to assessing the statistical significance of the results, their clinical or practical significance is also assessed using the appropriate statistics, it turns out to be practically zero... It can be assumed that the smaller the absolute size of a measured effect, the greater the likelihood that the effect is due to some extraneous, uncontrolled variable. In the REG experiments, statistical significance of the results is achieved only against a background of a very large number of trials, and the practical significance of the results is concomitantly zero. It can be, therefore, also assumed that such results are probably the outcome of one or more uncontrolled variable.[9]
According to the physicist Victor Stenger "While Schmidt claims positive results, his experiments also lack adequate statistical significance and have not been successfully replicated in the thirty-five years since his first experiments were reported."[10]
The psychologist James Alcock wrote that he found "serious methodological errors" throughout Schmidt's work which rendered his conclusions of psychokinesis untenable.[11] This included criticism of Schmidt acting both as experimenter and subject and lack of clarification and detail from his reports such as the possibility of optional stopping during the experiments.[12]
Schmidt has also drawn criticism for endorsing the psychic claims of Uri Geller.[13][14]
