Each semester Dr. Andes Azuero presents topics in statistical analyses and interpretation to the SON Faculty and Students.
The Stats Corner and Stats Seminar Series are designed to provide accessible and informative statistical education of a variety of topics that are of interest to faculty and students. The series is presented by Dr. Andres Azuero, Assistant Professor and Center for Nursing Research Statistician.
Dr. Andres Azuero, Assistant Professor and Center for Nursing Research Statistician
Be sure to attend the next Stats Seminar, May 7, 2010 @ 11:00 in the Center for Nursing Research.
A Note on Power Calculations…
The power of a statistical test is the probability of rejecting a null hypothesis (for instance, of no treatment effect) when the alternative is true (e.g.; the treatment actually works). More often than not, the sample size for a study is restricted by a budget. In such cases, power calculations at the design stage of a study provide crucial information regarding the magnitude of the effects that investigators can expect to detect if present. Often times, a calculation under simplified assumptions is sufficient. Standard software is readily available for a variety of simple statistical models. More complex designs may require even simulations. Assuming a fixed sample size constrained by a budget, for quick calculations of detectable differences between two groups (treatment vs. control, or exposed vs. non-exposed, or younger vs. older, etc.) a few items are needed. The first thing needed is to define a primary outcome of interest. Usually continuous or binary outcomes are selected. Second, an attrition rate is needed in order to calculate the effective sample size. The third item needed is the proportion of participants each group or “allocation ratio”. The combination that achieves greatest power is equal numbers on each group, which is standard practice in experimental trials but not necessarily possible in observational studies. For continuous outcomes, an estimate of standard deviation is needed. For binary outcomes, a reference proportion is needed. With this information in hand, power and significance are set at the traditional levels of 0.8 and 0.05 and an estimate of detectable difference can be rapidly calculated. More complex designs such as repeated measures models or group-randomized trials require a little more information.
Remember that as part of its mission the CNR offers statistical consulting services such as power and sample size calculations for grant proposals and manuscripts.
The Research Interest Groups (RIGs) are designed to help faculty to develop networks and collaborations in a special research or scholarship areas. The RIGs are open to all interested faculty, students and staff.
Behavioral RIG: Chair- Linda Moneyham, PhD, RN, FAAN
The purpose of the Behavioral Research Interest Group is to provide a forum for discussion of topics and issues related to research of behavior as it relates prevention of illness, health promotion, and maintenance and restoration of health in the context of illness. Particular interests of the group include behavioral theories supportive of nursing interventions, high risk populations and health disparities, and research design and methods for community-based research.
Biobehavioral RIG: Chair-Marti Rice, PhD, RN
The purpose of the Biobehavioral RIG is to share resources and facilitate research on biobehavioral interactions in relation to various health outcomes. The key activities addressed by this RIG are writing a group paper on stress and inflammation, sustaining a journal club for discussion of conceptual and methodological issues in biobehavioral research and responding to member requests for review of research proposals and manuscripts.
Intervention Research, Technology and Population Science RIG- Patrick McNees, PhD, FAAN
This is a multi-disciplinary forum for individuals interested in developing and validating the effects of multi-component intervention packages or performing large-scale population-based studies. This group is also for individuals interested in use of technological research tools and applications. Specific areas of interest may be as specific as cancer or as general as community-based education and support delivery systems. The group will support investigators from idea formulation, pilot work and methodological considerations to funding support.
Writer’s Interest Group: Chair-Teena McGuinness, PhD, RN
The purpose of the Writer’s Interest Group is to encourage the writing of faculty, students, and staff through supportive interaction. Popular recurring topics include addressing reviewers’ comments, knowing when the paper is “good enough” to submit, and resources for developing writing skills.