| E.S.P. | Extra-Sensory Perception. Perception without the function of the recognized senses. |
| P.T. | Pure telepathy; that is, extra-sensory perception of the mental processes of another person. ‘Pure’ refers to the absence of objective representation of the mental act or image, which might permit of clairvoyance by the percipient. |
| P.C. | Pure clairvoyance; extra-sensory perception of objective facts. Pure’ refers to the elimination of telepathy from the experimental situation. |
| B.T. | Clairvoyant card calling, with shuffled and cut pack of 25 cards placed face down before the percipient. He calls the top card and the call is recorded and the card removed. After 5 calls, or after the entire 25, the calls are checked against the inverted pile of called cards. B.T.-5 represents the condition of checking after every 5 calls; B.T.-25, after the whole pack. |
| D.T. | Clairvoyant card calling, with the cut pack of cards remaining unopened until after the 25 calls are made. Calling 'down through5, without removing the card called until the end of the run of 25. |
| D or Dev. | Deviation from mean chance expectation (np). |
| np | Number of trials multiplied by the probability of succeeding on each trial, which gives the mean chance expectation. (This and the following abbreviations are more fully explained in the Appendix to Chapter II) |
| p.e. | Probable Error of np. This is the deviation from up at which the odds are even that it was or was not due to mere chance. |
| X | This is the value of the deviation divided by the p.e. When the deviation is 4 times the p.e. (X=4) or more, the deviation is regarded as ‘significant', i.e. reliably showing a principle beyond ‘chance’ activity. |
