The observational units are what you take measurements on. In many experiments they are the same as the experimental units. Then you can simply say so. In the waking example the observational units are the experimental units.
Of course, you need to know what you are going to measure before you can say what objects you are going to measure, so fill in the What measurements are to be recorded? box at the same time as this one.
In the example where 12 students are used for 5 days, if each student is measured once at the end of the experiment then the observational units are the 12 students; if each student is measured at the end of each day then the observational units are the 60 student-days. In the bees example, if the grower counts the number of apples on each tree then the observational units are the trees.
On the data sheet, there is usually one row for each observational unit.
It is helpful to state the number of observational units, especially if they are not the same as the experimental units.
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Page maintained by R. A. Bailey
Page updated 17/11/01