Decision boundaries and receiver operating characteristic curves: new methods for determining accelerometer cutpoints

We propose and evaluate the utility of an alternative method (decision boundaries) for establishing physical activity intensity-related accelerometer cutpoints. Accelerometer data collected from seventy-six 11- to 14-year-old boys during controlled bouts of moderate- and vigorous-intensity field physical activities were assessed. Mean values and standard deviations for moderate- and vigorous-intensity activities were obtained and normal equivalents generated. The decision boundary (the point of intersection of overlapping distributions) was used to create a lower-bound vigorous-intensity cutpoint. Receiver operating characteristic (ROC) curves compared the sensitivity and specificity of the new cutpoint and mean values with the actual activity. There was a 96.5% probability that participants performing vigorous-intensity physical activity were accurately classified when using the decision boundary of 6700 counts per minute, in contrast to the 50% accurately classified when the mean value was used. Inspection of the empirical ROC curve indicated that the decision boundary provided the optimal threshold to distinguish between moderate and vigorous physical activity for this dataset. In conclusion, decision boundaries reduced the error associated with determining accelerometer threshold values. Applying these methods to accelerometer data collected in specific populations will improve the precision with which accelerometer thresholds can be identified.     

Using a Behavior Change Model to Document the Impact of Visits to Disney's Animal Kingdom: A Study Investigating Intended Conservation Action

Abstract Over the last 10 to 15 years, zoos and aquariums have set out to influence visitors' conservation‐related knowledge, attitudes, affect, and behavior. In 2000, the Institute for Learning Innovation collaborated with Disney's Animal Kingdom (DAK) on a comprehensive baseline study conducted to assess the outcomes of a DAK experience on visitors in four areas: knowledge, attitudes, affect, and behavior. This article describes one aspect of the comprehensive study: an investigation of the long‐term (two‐to‐three‐month) impact of a visit to Conservation Station at Disney's Animal Kingdom on visitors' intended conservation action. The study used a behavior change model from the health arena: the Prochaska Model of Behavioral Change. The model proved helpful but had some drawbacks, suggesting the need to develop a more sensitive change model. The implications of this study could assist institutions in thinking about what audiences or messages to emphasize in order to influence behavior.     

Psychometric Characteristics of the Revised Procrastination Inventory

The Procrastination Inventory developed for use with doctoral students in clinical psychology was modified for use with ABD students and doctoral graduates in a College of Education. The original Procrastination Inventory contained 43 items with 11 subscales. The structure of the revised measure was analyzed both through factor and Rasch analyses and three subscales that were more generalized were found instead of the eleven originally posited. The three subscales were: (1) procrastination, 20 items, alpha = .88, (2) perfectionism, 9 items, alpha = .64, and (3) graduate school comfort, 6 items, alpha = .59. Eight items were deleted after Rasch and factor analyses, resulting in a 35-item scale. Validity was demonstrated by the measure's ability to predict dissertation completion and through correlations with related measures. The Procrastination Inventory is useful in the study of attrition from doctoral programs, particularly at the dissertation stage.