Glossary O

One-group pretest-posttest design refers to a non-experimental design in which a single group is tested, exposed to only one level of an independent variable, and then retested; a non-experimental design involving one measurement before treatment and one measurement after treatment for a single group of participants.

One-person trap is when the consequences of a destructive behavior affect only the individual, such as overeating
One-to-one intervention to help the bereaved are programs that draw on those who have previously been bereaved or on trained laypersons to help bereaved persons

One-to-one principle is a counting principle that states that there must be one and only one number name for each object counted

One-trial learning refers to Guthrie's contention that the association between a pattern of stimuli and a response develops at full strength after just one pairing of the two (2).
Oneiromancy is defined as the practice of predicting the future by interpreting dreams.

Oniomania means excessive, uncontrollable desire to buy things.