The Equivalent Time-Samples Design can be conceptualized as follows:
In actual practice, you do not regularly alternate X1 (intervention) with X0 (control); rather, the selection of X1 or X0 should be determined randomly.
This design is useful when there is reason to suspect that the experimental intervention produces results that are transient or reversible in character. There is only one participant group (or even just one participant, in N of 1 studies). On one occasion the experimental treatment is applied. On another occasion an alternate treatment, or no treatment, is applied. In our diabetes example, perhaps you suspect that the blood sugar reading is dependent on the treatment (educational or persuasive approach) during the patient's last visit to the office. If the standard approach was used, the reading will be high. If the new approach was used, the reading will be low. That is, you suspect that the effect of your new treatment (educational or persuasive) protocol is easily reversed. This design could be useful in testing such a hypothesis.
Return to quasi-experimental designs.