Final answer:
The study in question is a phenomenological study, an observational and nonexperimental approach focused on understanding experiences through interviews.
Step-by-step explanation:
The study described by the student, where data was primarily collected through interviews about the experience of parenting a child with a heart transplant, is known as a phenomenological study. This type of study falls under the broader category of observational studies, which are types of nonexperimental scientific investigations. The focus is on understanding and describing experiences without manipulating any variables.