Signal-acquisition time also affects the sample rate of the scope.
Sample Rate = Memory Depth/Acquisition Time
Memory depth of the scope can be small or large depending on what scope you have. The acquisition time is set by adjusting the time-per-division setting on the oscilloscope. As the acquisition time increases, the sample rate will have to decrease in order to fit the entire acquisition into the scope’s memory. Having an appropriate sample rate for time-dependent measurements (frequency, pulse width, rise time, etc.) is important.
He tackles signal vertical and horizontal scaling and resolution (bits) too in the article. Increasing the vertical scaling of the signal enabled a much more accurate VPPmeasurement with a standard deviation that’s 15 times smaller.
Read the whole article here: (http://electronicdesign.com/test-measurement/make-great-oscilloscope-measurements)