Using classification and regression tree modelling to investigate response shift patterns in dentine hypersensitivity

BACKGROUND: Dentine hypersensitivity (DH) affects people's quality of life (QoL). However changes in the internal meaning of QoL, known as Response shift (RS) may undermine longitudinal assessment of QoL. This study aimed to describe patterns of RS in people with DH using Classification and Regression Trees (CRT) and to explore the convergent validity of CRT with the then-test and ideals approaches. METHODS: Data from an 8-week clinical trial of mouthwashes for dentine hypersensitivity (n = 75) using the Dentine Hypersensitivity Experience Questionnaire (DHEQ) as the outcome measure, were analysed. CRT was used to examine 8-week changes in DHEQ total score as a dependent variable with clinical status for DH and each DHEQ subscale score (restrictions, coping, social, emotional and identity) as independent variables. Recalibration was inferred when the clinical change was not consistent with the DHEQ change score using a minimally important difference for DHEQ of 22 points. Reprioritization was inferred by changes in the relative importance of each subscale to the model over time. RESULTS: Overall, 50.7% of participants experienced a clinical improvement in their DH after treatment and 22.7% experienced an important improvement in their quality of life. Thirty-six per cent shifted their internal standards downward and 14.7% upwards, suggesting recalibration. Reprioritization occurred over time among the social and emotional impacts of DH. CONCLUSIONS: CRT was a useful method to reveal both, the types and nature of RS in people with a mild health condition and demonstrated convergent validity with design based approaches to detect RS

Influence of using alternative means on type-i error rate in the comparison of independent groups

In this study, the effect of using trimmed, winsorized, and modified means instead of arithmetic mean on type-I error rate was investigated when the assumptions of the one-way ANOVA were not satisfied. Therefore, random numbers were generated by simulation technique from the populations distributed by Normal (0,1), Beta (5,2) and ?2 (3) for 3 and 4 groups. The results of 30 000 simulation trials demonstrated that all the means displayed similar type-I error rates when the variances were homogenous regardless of the distribution shape, sample size and the number of groups. When homogeneity of variances assumption was not satisfied, the most reliable result was obtained by using trimmed mean in terms of keeping the type-I error rate at nominal alpha level and it was followed by modified and winsorized means. The most biased results were obtained when arithmetic mean was used

Effect of stocking density on deviation from bilateral symmetry and slaughter weight in broilers

The main objective of this study was to investigate the effect of two different stocking densities (11 birds/m2 and 17 birds/m2) on deviation from bilateral symmetry in broiler chickens. For this purpose, the weekly body weight, left and right shank length, shank width, wing length, face width and face length of the same birds were measured on from 7th to 42nd days of age. Repeated measurements analysis of variance was used to investigate the effect of stocking densities and ages (week) on relative asymmetry. Binary logistic regression analysis was used to determine the most important morphological character influencing the deviation from ideal slaughter weight of 1800 g. The overall relative asymmetry mean for shank width was significantly greater in control group (2.42±0.41) than in treatment group (1.87±0.43). The results of binary logistic regression analysis showed that only increase in difference of width in left and right shank caused significant change (p=0.0148) in slaughter weight. In this study, the deviation from the bilateral symmetry was mostly found in fluctuating asymmetry for the measured characters in treatment group (11 birds per m2), and the low fluctuating asymmetry level was generally indicated higher welfare level and lower developmental instability for this group than that of the control group (17 birds per m2). Stocking density can be stated as one of the most important environmental factors which may influence developmental stability, welfare and performance of broilers

Eine Bewertung der Zeitpunkte embryonaler Sterblichkeit beim Chukarhuhn (Alectoris chukar) anhand des Klassifikationsbaum-Verfahrens

Classification tree method is a potentially powerful tool to predict membership of cases in the classes of a categorical dependent variable. The use of classification tree is not widespread in the fields of agriculture. Egg weight, shell thickness, shell weight, shell ratio, egg width, egg length, egg volume, shell surface area were chosen for investigating of their influence on embryonic mortality stages in fertilized eggs of Chukar partridge. All measured and calculated egg parameters were analyzed by classification tree method in this study. According to CTM, the embryonic mortality stages were affected by egg weight (EW), egg volume (EV), blunt-edge shell thickness (BST) and average shell thickness (AST). EW appeared as root terminal node at the classification tree. Embryonic mortality stages were influenced by EV when EW was less than 22.1 g and by BST when EW was greater than 22.1 g. EEM occurred more often than MEM and LEM when EW was less than 22.1 g. However, when EW was higher than 22.1 g, LEM was higher than EEM and MEM. When EW and BST were higher than 22.1 g and 22.3 ?, respectively, LEM was about 80.0%. EEM was about 81.2% when EW was less than 22.1 g and EV was higher than 25.1. EEM and LEM occurred but MEM did not occur when AST was higher than 22.3 ?m. CTM estimated with an accuracy of 75.6% that EW, EV, BST, and AST primarily affected embryonic mortality stages. Finally, the results of this study showed that this method could be used in the fields of agriculture. © Verlag Eugen Ulmer, Stuttgart