It is common for clinicians to report on groups of people who have been given a particular treatment, particularly when it is a new or uncommon one for that treatment setting or for a specific range of problems. This is how progress is made in clinical practice.

A series of people with similar problems (meeting the criteria for impressive single case studies) who respond to spiritual healing will be even more impressive. This is usually difficult to organize without the collaboration of a health care professional.

A series of people with different problems responding to healing is helpful in demonstrating the spectrum of healing abilities of a given healer or healing approach. A healer will often find that people with particular problems respond to her or his treatments, while people with other problems do not respond. Healees may find that they have a dramatic response to one of a series of treatments, with more modest or minimal responses to other treatments from the same healer.

With a sufficiently large number of subjects with chronic disease, it is possible to measure changes from before to after treatment and run statistical analyses on the results. The assumption would be that with chronic disease the symptoms are likely to remain unchanged over time, so significant changes might be attributed to the healing treatments. However, without a control group, the skeptics will always raise questions as to whether these results could have occurred by chance or could be due to some unnoticed agents other than the healing.