Asymptotic bias in the linear mixed effects model under non-ignorable missing data mechanisms

Summary.  In longitudinal studies, missingness of data is often an unavoidable problem. Estimators from the linear mixed effects model assume that missing data are missing at random. However, estimators are biased when this assumption is not met. In the paper, theoretical results for the asymptotic bias are established under non-ignorable drop-out, drop-in and other missing data patterns. The asymptotic bias is large when the drop-out subjects have only one or no observation, especially for slope-related parameters of the linear mixed effects model. In the drop-in case, intercept-related parameter estimators show substantial asymptotic bias when subjects enter late in the study. Eight other missing data patterns are considered and these produce asymptotic biases of a variety of magnitudes.     

An Evaluation of Stimulus Preference Assessment Methodology in Organizational Behavior Management

The organizational behavior management literature has yielded few stimulus preference assessment methodologies for use with employees. The current investigation compared three preference assessments (ranking, survey, and multiple stimulus without replacement procedures) found in the organizational behavior management literature for their ability to predict reinforcers for direct care staff members’ behavior. In the first experiment all assessments were effective for predicting reinforcers, but the results were limited by a lack of control items in the assessment. In the second experiment the survey and ranking assessments both proved to be effective for identifying reinforcers and neutral or ineffective stimuli. Implications of these results and directions for future research are discussed.     

Projective (2n,n,λ,1)-designs

A projective (2n,n,λ,1)-design is a set $\text{D}$ of n element subsets (called blocks) of a 2n-element set V having the properties that each element of V is a member of λ blocks and every two blocks have a non-empty intersection. This paper establishes existence and non-existence results for various projective (2n,n,λ,1)-designs and their subdesigns.     

Assumptions of social mobility research in the U.S.: The case of occupational status

This paper examines the theoretical and empirical basis for common rank-orderings of occupational roles by raters throughout the world. From an illustrative comparison of occupational stratification in Australia and the United States we conclude tentatively that (1) commonalities in the socioeconomic characteristics of occupational roles provide the basis for interplace consistencies in “prestige” scores, (2) the structure of occupational mobility in the U.S. and Australia is largely similar, (3) this similar structure of occupational stratification manifests a common socioeconomic process which defines a (the?) major component of occupational mobility in capitalist, industrial (only?) societies. We infer that “prestige” scores for occupations are fallible estimates of the socioeconomic statuses of occupation, within the context of mobility processes in (at least) the U.S. and Australia.     

The program effect of batterer programs in three cities

Recent meta-analyses and experimental designs of batterer program evaluations suggest little or no program effect. This finding may be compromised by a variety of analytical issues. Instrumental variable analysis addresses some of these issues, especially the relationship of program dropout to batterer reassault. This method of analysis was, therefore, used to test for program effect in a multi-site evaluation. The sites were three well-established batterer programs using a gender-based, cognitive-behavioral approach (n = 640). Completing a batterer program reduced the likelihood of reassault by 44% to 64%, depending on the specification used. Completing a 3-month program appeared to be as effective as completing a 5 1/2- or 9-month program. This moderate effect is an accomplishment considering the problems associated with the program participants and the inconsistency in the criminal justice system at the research sites. The findings remain tentative because of weak instrumental variables for reassault, but do confirm the need for more complex analyses of program effect.     

Psychiatric inpatients' experience of nursing observation. A United Kingdom perspective

1. Nursing observation is a key component of psychiatric inpatient nursing care. 2. Patients' experiences of being observed are strongly influenced by the attitudes and behaviors of the observing nurses. 3. Patients prefer to be observed by nurses they know and who talk to them.