A research assistant in a lab conditions dogs to salivate to the sound of a bell. During conditioning, the assistant deliberately manipulates the interval between the sound of the bell and the presentation of food. After conditioning, he measures how much the dog salivates when the bell is presented alone. The interval is the variable. The amount of salivation is the variable.

the interval is the independant variable, the amount of salivation is the dependant variable

Explanation: see, the interval isn't whats going to change, it stays the same, the dogs salivation however can change and in the pavlov experiment it did change, so that one is the dependant variable

i honestly speaking this is too long

dude you should crop your image so only the question shows. but   can you explain it better