PSYCHOTHERAPY ENGAGERS VERSUS NON-ENGAGERS

Chapter 4: Method
The present study examined therapist helping skills across thirds of intake
sessions (1 st , 2 nd , and 3 rd thirds) and across engagement condition (engager vs. non-
engager). The design of the present study is a quantitative descriptive field design.
Power Analyses
Power analyses for 2-tailed t-tests indicated that for a large effect size, d = 0.8, at
an alpha level of .05, 52 participants (26 engagers, 26 non-engagers) would be needed for
80% power. With the same expected effect size, d = 0.8, and same power level of 80%,
but changing the alpha level to .10, 40 clients (20 engagers, 20 non-engagers) would be
needed. With the same effect size of .8 and power of 80%, but an alpha of .20, 30 clients
would be needed (15 engagers, 15 non-engagers). Effect sizes from Tryon (2003)
indicated very large effects for closed questions, d = 2.86, and information, d = 3.29.
Using the effect size d = 2.86, and alpha = .10, 6 clients (3 engagers, 3 non-engagers)
would be needed to have 80% power. Using the effect size d = 3.29, and alpha = .10, 6
clients (3 engagers, 3 non-engagers) would be needed to have 80% power. The present
study, with 8 dropouts and 8 continuers, has 84.5% power to detect effects of d = 1.4 at
an alpha level of .10 when such effects indeed exist. Thus, the present sample size
provides sufficient power for detecting very large effects (d = 1.4) at alpha levels of .10.
Participants and Setting
Setting. The present study utilized data collected in the Maryland Psychotherapy
Clinic and Research Lab (MPCRL), a mental health clinic providing individual
psychodynamic/interpersonal psychotherapy to adults from the local community. One of
the main purposes of the clinic was to collect data for psychotherapy research; thus, all
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