decreasing / effect size / effect size conventions / increasing / liberal / meta-analysis / power tables / statistical power / stringent / .20 / .50 / 80 / practically / statistically / stringent / one-tailed / two-tailed In the last chapters, a group of psychologists conducted a study in which a student attended a one hour counseling session each week for six weeks that was designed to help the student reduce stress. Based on the results of this study, the psychologists have conducted a larger study in which 30 freshmen attended the counseling sessions. Now the psychologists are planning studies in which they will use sample data to estimate population values. As an initial step in their planning, the psychologists have referred to a study that combines the results of many other studies of activity levels among depressed people. This study is an example of a (1) and its primary data are obtained by calculating the (2) of each study reviewed. As they continue planning, the psychologists discuss their desire to conduct a study that will yield a statistically significant result when the research hypothesis is true. These discussions are about the (3) _ As guidelines for planning this aspect of their studies, the psychologists can use Cohen's (4) . Different studies may have different effects on their participants, and may include different numbers of participants. Therefore, the psychologists may obtain more precise estimates of this aspect of their studies by using (5) According to Cohen's conventions for assessing the power of a study, a small effect size is (6) , a medium effect size is (7) , and a large effect size is (8) Cohen has also expressed the opinion that investigators should plan studies to have a power of (9) _. In order to increase the power of their statistical analysis, the psychologists might _the size of their sample, using a less (11) test. However, if the psychologists use a very large sample that results in a small, but (13)_ _ significant, increase in the average number of activities o daily living performed after a treatment like group therapy, their results may not be (14 significant