The amount of flow through a solenoid valve in an automobile’s pollution-control system is an important characteristic. An experiment was carried out to study how flow rate depended on three factors:...

The amount of flow through a solenoid valve in an automobile’s pollution-control system is an important characteristic. An experiment was carried out to study how flow rate depended on three factors: armature length, spring load, and bobbin depth. Two different levels (low and high) of each factor were chosen, and a single observation on flow was made for each combination of levels.

a. The resulting data set consisted of how many observations?

b. Does this study involve sampling an existing population or a conceptual population?