The fit of empirical data to two latent trait models.

The study explored fit of empirical data to the Rasch and three-parameter logistic latent trait models focusing upon the relationship between deviations from latent trait model assumptions and fit. The study also investigated estimation precision for small sample and short test conditions and evaluated parameter estimation costs for the two latent trait models. Rasch and three-parameter abilities and item parameters were estimated for twenty-five 40-item tests having 1000 examinees. These estimated parameters were substituted for true parameters to make predictions about number-correct score distributions using a theorem by Lord (1980) equating ability with the conditional distribution of number correct scores. Predicted score distributions were compared with observed score distributions by Kolmogorov-Smirnov and Chi square measures, and with graphical techniques. The importance of three latent trait model assumptions: unidimensionality, equality of item discrimination indices, and no guessing were assessed with correlation analyses. Estimation precision for short 20-item tests and for small samples of 250 examinees were evaluated with correlation methods and by assessing average absolute differences between estimates. Simple summary statistics were gathered to evaluate computer cost and time for parameter estimation with each model. The Rasch and the three-parameter models both demonstrated close fit to the majority of data studied. Eighty percent of tests fit both models quite well. Only one predicted test distribution deviated significantly from the observed score distribution. Results obtained with the Chi square measure were less favorable toward the models than Kolmogorov-Smirnov assessments had been. This outcome was attributed to the apparent sensitivity of the Chi square statistic to lack of normality in score distributions. Graphic results clearly supported statistical measures of fit leading to the conclusion that latent trait models adequately describe empirical test sets. The Rasch model fit data, overall, as well as the three-parameter model. The average K-S statistic for 25 tests was 1.304 for the Rasch model and 1.289 for the three-parameter model. The latter model fit data better than the Rasch model for 65 percent of the tests, yet the differences in fit between the models were insignificant. The Chi square measure and graphical tests supported these results. Lack of unidimensionality was the primary cause for misfit of data to the models. Correlations between fit statistics and indices of unidimensionality were significant at the .05 probability level for the Rasch and three-parameter models. When item discrimination parameters were unequal, fit of data to both models was impaired, and when guessing was present, while not well estimated on samples of 1000, fit of data to both latent trait models tended to be distorted. Ability estimates from short 20-item tests were quite precise, especially for the Rasch model. Correlations between ability estimates from the 20-item and longer tests were .923 for the Rasch estimates, and .866 for the three-parameter estimates. Difficulty estimates made from small 250 examinee samples were also quite precise, but estimates of other item parameters from small samples tended not to be very accurate. Although small sample item discrimination estimates were reasonable, estimates of the guessing parameter were very poor. The results suggest that at least 1000 examinees are required to obtain precise estimates with the three-parameter model. The average cost for estimating Rasch item parameters and abilities was only $12.50 for 1000 examinees in contrast to$35.12 for the three-parameter model, but when item parameters were known in advance, and only abilities estimated, these cost differences disappeared

Pyramiding of Meloidogyne hapla resistance genes in potato does not result in an increase of resistance

High levels of resistance against Meloidogyne hapla have been identified in wild species of tuber-bearing potatoes, but only QTL with partial effects have been identified so far in back crosses with cultivated potato. This study was designed to test if pyramiding of two previously identified resistance genes, R Mh-tar and R Mh-chc A, will result in improved or even an absolute level of resistance. R Mh-tar and R Mh-chc A introgressed from the wild tuber-bearing potato species Solanum tarijense and Solanum chacoense were combined in a segregating diploid Solanum tuberosum population. With the aid of AFLP markers, descendants from this segregating population were classified into four groups, carrying no R gene, with only R Mh-tar , with only R Mh-chc A and a group with the pyramided R Mh-tar and R Mh-chc A. Upon inoculation with M. hapla isolate Bovensmilde, the group containing only R Mh-chc A showed a decline of 88% in average number of developed egg masses compared to the group without R Mh-chc A and R Mh-tar . The group of genotypes containing only R Mh-tar , but not R Mh-chc A, showed a decline of 55% in the number of developed egg masses compared to the group without R Mh-chc A and R Mh-tar . Unfortunately, the latter effect of R Mh-tar was not significant. The effect of both loci, R Mh-tar and R Mh-chc A combined, did not further reduce the number of egg masses compared to the level of R Mh-chc A alon

Biosignal and context monitoring: Distributed multimedia applications of body area networks in healthcare

We are investigating the use of Body Area Networks (BANs), wearable sensors and wireless communications for measuring, processing, transmission, interpretation and display of biosignals. The goal is to provide telemonitoring and teletreatment services for patients. The remote health professional can view a multimedia display which includes graphical and numerical representation of patients’ biosignals. Addition of feedback-control enables teletreatment services; teletreatment can be delivered to the patient via multiple modalities including tactile, text, auditory and visual. We describe the health BAN and a generic mobile health service platform and two context aware applications. The epilepsy application illustrates processing and interpretation of multi-source, multimedia BAN data. The chronic pain application illustrates multi-modal feedback and treatment, with patients able to view their own biosignals on their handheld device

Daily physical activity patterns in cancer survivors: a pilot study

In cancer survivors physical activity levels are measured primarily with questionnaires. As a result, insight in actual physical activity patterns of cancer survivors is lacking. Activity monitoring with accelerometers revealed that cancer survivors have lower levels of physical activity in the afternoon and early evening. This finding can help to personalize physical activity advice more adequately for these patients

Targeting the Beta-2-Adrenergic Receptor and the Risk of Developing Alzheimer's Disease:A Retrospective Inception Cohort Study

BACKGROUND: Animal studies suggested that β2-Adrenergic receptors (β2AR) may be a potential target for the treatment of Alzheimer's disease (AD). OBJECTIVE: This retrospective inception cohort study aimed to assess the association between antagonists and agonists of the β2AR and the risk of starting treatment for AD in older adults. METHODS: A retrospective inception cohort study was conducted among older adults who initiated either non-selective βAR antagonists or selective β2AR agonists using the University Groningen IADB.nl prescription database (study period 1994-2019). For each exposed cohort, two reference cohorts (A and B) were matched on age at index date. The main outcome was defined as at least two prescriptions for cholinesterase inhibitors (rivastigmine, galantamine, and donepezil) and/or memantine. Cox proportional hazard regression models were used to estimate hazard ratios (HR). RESULTS: The risk of developing AD was elevated among patients exposed to non-selective βAR antagonists (A: aHR 3.303, 95% CI 1.230-8.869, B: aHR 1.569, 95% CI 0.560-4.394) and reduced among patients exposed to selective β2AR agonists (A: aHR 0.049, 95% CI 0.003-0.795, B: aHR 0.834, 95% CI 0.075-9.273) compared to reference patients. CONCLUSION: These findings suggest that exposure to non-selective βAR antagonists is associated with an increased risk for developing AD whereas there may be a decreased risk for developing AD after exposure to selective β2AR agonists

Are processes in acceptance & commitment therapy (Act) related to chronic pain outcomes within individuals over time? : an exploratory study using n-of-1 designs

Acknowledgements The authors would like to thank the European Health Psychology Society for providing a grant that enabled the collaboration of the co-authors for this article. Author contributions HT designed the study, organized the data collection, carried out the statistical analyses and drafted the first version of the manuscript. DJ and MJ supervised the statistical analyses and were actively involved in writing and revising the manuscript. MVH and KS designed the study and were actively involved in writing and revising the manuscript. All authors read and approved the final manuscript.Peer reviewedPublisher PD