What is the independent and dependent variable in this experiment?

Each participant was assigned a written version of a service scenario to read in its entirety. For the positive (negative) service experience, subjects were provided with a scenario in which they were seated immediately (15minutes) after arrival; had an attentive (distracted) waitress; received prompt (slow) service; and consumed delicious (overcooked) meals. To control for the effect of extraneous situational variables, bill size, party size, server gender, payment method, and restaurant patronage were held constant in each scenario. After reading the assigned scenario, subjects were shown apieceofpaperwithacopyofoneofthreemealreceipts:areceiptwithnopersonalizedmessage (i.e.,blank),areceipthavingapersonalized"Thanks"messagewithasignature,orareceipthaving a personalized "Thanks" message with a smiley face. While keeping in mind personal experiences, subjects were asked to provide a tip perceived to be fair based on the quality of service described inthe scenario. Finally, subjects were asked items assessing the quality of service described in the scenario, general restaurant and food preferences, dining out frequency, and basic demographic information. A manipulation check revealed a significant difference in perceived quality of service between scenarios, F(1, 166)=198.68, p<0.001.[1]

Experimental conditions were assigned randomly across participants so that each combination of the stimuli (i.e., service scenario and receipt type) appeared to a similar number of individuals. Cell sizes rangedbetweenexperimentalconditions.Ofthe82subjectsassignedtothepositiveservice scenario, 28 received a receipt with no personalization message, 28 received a receipt with a personalized "Thanks" message and a signature, and 26 received a receipt with a personalized "Thanks"messageandasmileyface.Ofthe86subjectsassignedtothenegativeservicescenario, 27 received a receipt with no personalization, 30 received a receipt with a personalized "Thanks" message and a signature, and 29 received a receipt with a personalized "Thanks" message and a smiley face.