When visually inspecting time series analysis data, one examines level, trend, and variability, within each phase, comparing these for each phase with adjacent phases. If one attains a stable baseline with a flat trend and a level at about $4$ responses per hour; and then if one introduces an intervention procedure and there is an initial increasing trend, but the data path levels out at about $14$ responses per hour, and with no more bounce than was observed during baseline, one can conclude:

a$.$

The intervention has been effective

b$.$

There has been an increase in level

c$.$

The data are too variable to draw any conclusions.

d$.$

There has been an increase in level that may or may not have been brought about by the intervention