Incremental criterion prediction of personality facets over factors: obtaining unbiased estimates and confidence intervals

 Many researchers have argued that higher order models of personality such as the Five Factor Model are insufficient, and that facet-level analysis is required to better understand criteria such as well-being, job performance, and personality disorders. However, common methods in the extant literature used to estimate the incremental prediction of facets over factors have several shortcomings. This paper delineates these shortcomings by evaluating alternative methods using statistical theory, simulation, and an empirical example. We recommend using differences between Olkin-Pratt adjusted r-squared for factor versus facet regression models to estimate the incremental prediction of facets and present a method for obtaining confidence intervals for such estimates using double adjusted-. r-squared bootstrapping. We also provide an R package that implements the proposed methods.

Quantitative evaluation in health promotion : evaluation with confidence

Over the past 10 years or so, confidence intervals have become increasingly recognised in program evaluation and quantitative health measurement generally as the preferred way of reporting the accuracy of statistical estimates. Statisticians have found that the more traditional ways of reporting results - using P-values and hypothesis tests - are often very difficult to interpret and can be misleading. This is particularly the case when sample sizes are small and results are 'negative' (ie P>0.05); in these cases, a confidence interval can communicate much more information about the sample and, by inference, about the population. Despite this trend among statisticians and health promotion evaluators towards the use of confidence intervals, it is surprisingly difficult to find succinct and reasonably simple methods to actually compute a confidence interval. This is particularly the case for proportions or percentages. Much of the data which are analysed in health promotion are binary or categorical, rather than the quantities and continuous variables often found in laboratories or other branches of science, so there is a need for health promotion evaluators to be able to present confidence intervals for percentages or proportions. However, the most popular statistical analysis computer package among health promotion professionals, SPSS does not have a routine to compute a simple confidence interval for a proportion! To address this shortcoming, I present in this paper some fairly simple strategies for computing confidence intervals for population percentages, both manually and using the right computer software.

Application of sequential nonparametric confidence bands in finance

In a nonparametric setting, the functional form of the relationship between the response variable and the associated predictor variables is assumed to be unknown when data is fitted to the model. Non-parametric regression models can be used for the same types of applications such as estimation, prediction, calibration, and optimization that traditional regression models are used for. The main aim of nonparametric regression is to highlight an important structure in the data without any assumptions about the shape of an underlying regression function. Hence the nonparametric approach allows the data to speak for itself. Applications of sequential procedures to a nonparametric regression model at a given point are considered.

The primary goal of sequential analysis is to achieve a given accuracy by using the smallest possible sample sizes. These sequential procedures allow an experimenter to make decisions based on the smallest number of observations without compromising accuracy. In the nonparametric regression model with a random design based on independent and identically distributed pairs of observations (X ,Y ), where the regression function m(x) is given bym(x) = E(Y X = x), estimation of the Nadaraya-Watson kernel estimator (m (x)) NW and local linear kernel estimator (m (x)) LL for the curve m(x) is considered. In order to obtain asymptotic confidence intervals form(x), two stage sequential procedure is used under which some asymptotic properties of Nadaraya-Watson and local linear estimators have been obtained.

The proposed methodology is first tested with the help of simulated data from linear and nonlinear functions. Encouraged by the preliminary findings from simulation results, the proposed method is applied to estimate the nonparametric regression curve of CAPM.

Sequential fixed-width confidence bands for kernel regression estimation

We consider a random design model based on independent and identically distributed (iid) pairs of observations (Xi, Yi), where the regression function m(x) is given by m(x) = E(Yi|Xi = x) with one independent variable. In a nonparametric setting the aim is to produce a reasonable approximation to the unknown function m(x) when we have no precise information about the form of the true density, f(x) of X. We describe an estimation procedure of non-parametric regression model at a given point by some appropriately constructed fixed-width (2d) confidence interval with the confidence coefficient of at least 1−. Here, d(> 0) and 2 (0, 1) are two preassigned values. Fixed-width confidence intervals are developed using both Nadaraya-Watson and local linear kernel estimators of nonparametric regression with data-driven bandwidths.

The sample size was optimized using the purely and two-stage sequential procedure together with asymptotic properties of the Nadaraya-Watson and local linear estimators. A large scale simulation study was performed to compare their coverage accuracy. The numerical results indicate that the confidence bands based on the local linear estimator have the best performance than those constructed by using Nadaraya-Watson estimator. However both estimators are shown to have asymptotically correct coverage properties.

Sample size determination for kernel regression estimation using sequential fixed-width confidence bands

We consider a random design model based on independent and identically distributed pairs of observations (Xi, Yi), where the regression function m(x) is given by m(x) = E(Yi|Xi = x) with one independent variable. In a nonparametric setting the aim is to produce a reasonable approximation to the unknown function m(x) when we have no precise information about the form of the true density, f(x) of X. We describe an estimation procedure of non-parametric regression model at a given point by some appropriately constructed fixed-width (2d) confidence interval with the confidence coefficient of at least 1−. Here, d(> 0) and 2 (0, 1) are two preassigned values. Fixed-width confidence intervals are developed using both Nadaraya-Watson and local linear kernel estimators of nonparametric regression with data-driven bandwidths. The sample size was optimized using the purely and two-stage sequential procedures together with asymptotic properties of the Nadaraya-Watson and local linear estimators. A large scale simulation study was performed to compare their coverage accuracy. The numerical results indicate that the confi dence bands based on the local linear estimator have the better performance than those constructed by using Nadaraya-Watson estimator. However both estimators are shown to have asymptotically correct coverage properties.

The Integrated Model of Sport Confidence: A Canonical Correlation and Mediational Analysis

The main purpose of the study was to examine crucial parts of Vealey’s (2001) integrated framework hypothesizing that sport confidence is a mediating variable between sources of sport confidence (including achievement, self-regulation, and social climate) and athletes’ affect in competition. The sample consisted of 386 athletes, who completed the Sources of Sport Confidence Questionnaire, Trait Sport Confidence Inventory, and Dispositional Flow Scale-2. Canonical correlation analysis revealed a confidence-achievement dimension underlying flow. Bias-corrected bootstrap confidence intervals in AMOS 20.0 were used in examining mediation effects between source domains and dispositional flow. Results showed that sport confidence partially mediated the relationship between achievement and  self-regulation domains and flow, whereas no significant mediation was found for social climate. On a subscale level, full mediation models emerged for achievement and flow dimensions of challenge–skills balance, clear goals, and concentration on the task at hand.

Power, effects, confidence, and significance: an investigation of statistical practices in nursing research

Objectives: To (a) assess the statistical power of nursing research to detect small, medium, and large effect sizes; (b) estimate the experiment-wise Type I error rate in these studies; and (c) assess the extent to which (i) a priori power analyses, (ii) effect sizes (and interpretations thereof), and (iii) confidence intervals were reported. Design: Statistical review. Data sources: Papers published in the 2011 volumes of the 10 highest ranked nursing journals, based on their 5-year impact factors. Review methods: Papers were assessed for statistical power, control of experiment-wise Type I error, reporting of a priori power analyses, reporting and interpretation of effect sizes, and reporting of confidence intervals. The analyses were based on 333 papers, from which 10,337 inferential statistics were identified. Results: The median power to detect small, medium, and large effect sizes was .40 (interquartile range [. IQR]. = .24-.71), .98 (IQR= .85-1.00), and 1.00 (IQR= 1.00-1.00), respectively. The median experiment-wise Type I error rate was .54 (IQR= .26-.80). A priori power analyses were reported in 28% of papers. Effect sizes were routinely reported for Spearman's rank correlations (100% of papers in which this test was used), Poisson regressions (100%), odds ratios (100%), Kendall's tau correlations (100%), Pearson's correlations (99%), logistic regressions (98%), structural equation modelling/confirmatory factor analyses/path analyses (97%), and linear regressions (83%), but were reported less often for two-proportion z tests (50%), analyses of variance/analyses of covariance/multivariate analyses of variance (18%), t tests (8%), Wilcoxon's tests (8%), Chi-squared tests (8%), and Fisher's exact tests (7%), and not reported for sign tests, Friedman's tests, McNemar's tests, multi-level models, and Kruskal-Wallis tests. Effect sizes were infrequently interpreted. Confidence intervals were reported in 28% of papers. Conclusion: The use, reporting, and interpretation of inferential statistics in nursing research need substantial improvement. Most importantly, researchers should abandon the misleading practice of interpreting the results from inferential tests based solely on whether they are statistically significant (or not) and, instead, focus on reporting and interpreting effect sizes, confidence intervals, and significance levels. Nursing researchers also need to conduct and report a priori power analyses, and to address the issue of Type I experiment-wise error inflation in their studies. © 2013 .

Quantitative evaluation in health promotion : What's the difference?

This is the third in a series of articles on quantitative evaluation in health promotion written by Damien Jolley for the Health Promotion Journal of Australia. The first of these articles, published in the December 2000 issue, discussed the ideas behind sample surveys and how they can be used to improve evaluation of health promotion initiatives.1 The second, in the April 2001 issue, discussed confidence intervals in more detail and presented some strategies for computing confidence intervals for population percentages, both manually and using appropriate computer software. 2

Energy, protein, calcium, vitamin D and fibre intakes from meals in residential care establishments in Australia

Residents from high level (nursing homes) and low-level care facilities (hostel) being served the three common diet texture modifications (full diet, soft-minced diet and pureed diet) were assessed. Individual plate waste was estimated at three meals on one day. Fifty-six males and 156 females, mean age 82.9+/-9.5 (SD) years, of which 139 lived in nursing homes (NH) and 76 in hostels (H) were included. Mean total energy served from meals was 5.3 MJ/day, 5.1 to 5.6 MJ/day, 95% confidence intervals (CI), in NH which was less than in H, 5.9 MJ/day (CI 5.6 to 6.2 MJ/day) (P=0.007). Protein and calcium intakes were lower in NH, 44.5g (CI 41.5 to 47.5g), 359.0mg (CI 333.2 to 384.8mg), versus 50.5g (CI 46.6 to 54.3g), 480.5mg (CI 444.3 to 516.7mg) in H (P=0.017, P<0.001 respectively). There was no difference in nutrient/energy ratios, except for protein/energy, which was higher in NH 11.7 (CI 11.3 to 12.2) than in H 9.8 (CI 9.4 to 10.3) (P<0.001). Ability to self-feed had no significant effect on nutrient intakes in NH. The self fed group (N=63) had the following nutrient intakes: energy 4.0 MJ (CI 3.6 to 4.3 MJ), protein 44.6g (CI 40.3 to 48.9g), calcium 356.9mg (CI 316.3 to 397.4mg), fibre 14.9g (CI 13.2 to 16.5g). The assisted group (N=64) had the following nutrient intakes: energy 3.9MJ (CI 3.6 to 4.2MJ), protein 46.0g (CI 40.7 to 49.6), calcium 361.9mg (CI 327.8 to 396.1mg), fibre 14.9g (CI 13.2 to 16.1g). Of NH classified as eating impaired, 36% received no assistance with feeding and had lower intakes of protein 37.8g (CI 33.0 to 42.1g) compared to those receiving some assistance 46.1g (CI 41.3 to 50.9g) (P=0.026). Reduced energy intake accounted for the differences in nutrient intakes between nursing homes and hostels, except for protein. Strategies to effectively monitor nutrient intakes and to identify those with eating impairment are required in order to ensure adequate nutrition of residents in nursing homes and hostels.

Effect of creatine supplementation on housekeeping genes in human skeletal muscle using real-time RT-PCR

The present study examined the validity and reliability of measuring the expression of various genes in human skeletal muscle using quantitative real-time RT-PCR on a GeneAmp 5700 sequence detection system with SYBR Green 1 chemistry. In addition, the validity of using some of these genes as endogenous controls (i.e., housekeeping genes) when human skeletal muscle was exposed to elevated total creatine levels and exercise was also examined. For all except 28S, linear relationships between the logarithm of the starting RNA concentrations and the cycle threshold (C_T) values were established for ß-actin, ß2-microglobulin (ß₂M), cyclophilin (CYC), and glyceraldehyde-3-phosphate dehydrogenase (GAPDH). We found a linear response between C_T values and the logarithm of a given amount of starting cDNA for all the genes tested. The overall intra-assay coefficient of variance for these genes was 1.3% and 21% for raw C_T values and the linear value of 2^-C_T, respectively. Interassay variability was 2.3% for raw C_T values and 34% for the linear value of 2^-C_T. We also examined the expression of various housekeeping genes in human skeletal muscle at days 0, 1, and 5 following oral supplementation with either creatine or a placebo employing a double-blind crossover study design. Treatments were separated by a 5-wk washout period. Immediately following each muscle sampling, subjects performed two 30-s all-out bouts on a cycle ergometer. Creatine supplementation increased (P < 0.05) muscle total creatine content above placebo levels; however, there were no changes (P > 0.05) in C_T values across the supplementation periods for any of the genes. Nevertheless, 95% confidence intervals showed that GAPDH was variable, whereas ß-actin, ß₂M, and CYC were the least varying genes. Normalization of the data to these housekeeping genes revealed variable behavior for ß₂M with more stable expressions for both ß-actin and CYC. We conclude that, using real-time RT-PCR, ß-actin or CYC may be used as housekeeping genes to study gene expression in human muscle in experiments employing short-term creatine supplementation combined with high-intensity exercise.

Effects of timed voiding for the management of uninary incontinence in adults: systematic review

Aim: The aim of this paper is to present a systematic review assessing the effectiveness of timed voiding for the management of urinary incontinence in adults. Background: Despite the widespread use of systematic voiding programmes, their effectiveness is unclear, and the evidence for timed voiding has not been subject to rigorous and systematic evaluation. The impact on psychosocial factors and cost is also untested. The physiological basis for timed voiding is also poorly established. Methods: The systematic review incorporated the methodology of the Cochrane Collaboration. All randomized or quasi-randomized controlled trials that addressed timed voiding for the management of urinary incontinence in adults were searched, appraised, analysed and summarized. The date of the latest search was 2002. Data were extracted independently and appraised according to the level of concealment of random allocation prior to formal entry; few and identifiable withdrawals and dropouts and an analysis based on an intention to treat. The relative risk for dichotomous data was calculated with 95% confidence intervals. Where data were insufficient to support quantitative analysis, a narrative overview was undertaken. Results: Two trials of timed voiding met the inclusion criteria. In both, timed voiding was combined with other strategies. Participants were predominantly cognitively and physically impaired older women who resided in nursing home settings. Within-group improvements for the intervention groups were reported for both trials. One trial additionally reported a statistically significant reduction in night-time incontinence for the intervention group. The quality of the trials was modest and interpretation was limited by the potential for bias associated with inadequate concealment, missing data and no analysis by intention to treat. Conclusion: Terms used to describe voiding programmes that involve a fixed interval of voiding are variable. No conclusions can be drawn at this point about the effectiveness of timed voiding for the management of urinary incontinence in adults.

Validation of a food-frequency questionnaire assessment of carotenoid and vitamin E intake using weighed food records and plasma biomarkers: the method of triads model.

Background: Reliability or validity studies are important for the evaluation of measurement error in dietary assessment methods. An approach to validation known as the method of triads uses triangulation techniques to calculate the validity coefficient of a food-frequency questionnaire (FFQ).

Objective: To assess the validity of an FFQ estimates of carotenoid and vitamin E intake against serum biomarker measurements and weighed food records (WFRs), by applying the method of triads. Design: The study population was a sub-sample of adult participants in a randomised controlled trial of b-carotene and sunscreen in the prevention of skin cancer. Dietary intake was assessed by a self-administered FFQ and a WFR. Nonfasting blood samples were collected and plasma analysed for five carotenoids (a-carotene, b-carotene, b-cryptoxanthin, lutein, lycopene) and vitamin E. Correlation coefficients were calculated between each of the dietary methods and the validity coefficient was calculated using
the method of triads. The 95% confidence intervals for the validity coefficients were estimated using bootstrap sampling.

Results: The validity coefficients of the FFQ were highest for a-carotene (0.85) and lycopene (0.62), followed by b-carotene (0.55) and total carotenoids (0.55), while the lowest validity coefficient was for lutein (0.19). The method of triads could not be used for b-cryptoxanthin and vitamin E, as one of the three underlying correlations was negative.

Conclusions: Results were similar to other studies of validity using biomarkers and the method of triads. For many dietary factors, the upper limit of the validity coefficients was less than 0.5 and therefore only strong relationships between dietary exposure and disease will be detected.

Habit retraining for the management of urinary incontinence in adults (review)

Background
Habit retraining is toileting assistance given by a caregiver to adults with urinary incontinence. It involves the identification of an incontinent person's natural voiding pattern and the development of an individualised toileting schedule which pre-empts involuntary bladder emptying.

Objectives
To assess the effects of habit retraining for the management of urinary incontinence in adults.

Search strategy
We searched the Cochrane Incontinence Group specialised register (9 May 2002), MEDLINE (January 1966 to February 2004), EMBASE (January 1980 to Week 18-2002), CINAHL (January 1982 to February 2001), PsychINFO (January 1972 to August 2002), Biological Abstracts (January 1980 to December 2000), Current Contents (January 1993 to December 2001) and the reference lists of relevant articles. We also contacted experts in the field, searched relevant websites and hand searched journals and conference
proceedings.

Selection criteria
All randomised or quasi-randomised controlled trials comparing habit retraining delivered either alone or in conjunction with another intervention for urinary incontinence in adults.

Data collection and analysis
Data extraction and quality assessment were undertaken by at least two people working independendy of each other. Any differences were resolved by discussion. The relative risks for dichotomous data were calculated with 95% confidence intervals. Where data were insufficient for a quantitative analysis, a narrative overview was undertaken.

Main results
Three trials with a total of 337 participants met the inclusion criteria, describing habit retraining combined with other approaches compared with usual care. Participants were primarily care-dependent elderly women with concurrent cognitive and/or physical impairment, residing in either a residential aged-care facility or in their own home. Outcomes included incidence and/or severity of urinary incontinence, the prevalences of urinary tract infection, skin rash and skin breakdown, cost and caregiver preparedness, role strain and burden. Caregivers found it difficult to maintain voiding records and to implement the toileting program. A 61% compliance rate was reported in one trial .

There were no statistically significant differences in the incidence and in the volume of incontinence between groups. Within group analyses did however show improvements on these measures. Reductions were also reported for the intervention group in one study for skin rash, skin breakdown and in caregivers' perceptions of their level of stress. Descriptive data on the. intervention suggests that habit retraining is a labour-intense activity. Electronic loggers, used as an adjunct to caregiver-delivered wet/dry checks, were reported as providing more accurate data than that from caregiver conducted wet/dry checks. To date, no analysis of the time and resources associated with these comparisons is available.

Reviewers' conclusions
Data on habit retraining are few and of insufficient quality to provide a firm basis for practice.

Timed voiding for the management of urinary incontinence in adults (Review)

Background
Timed voiding is a fixed time interval toileting assistance program that has been promoted for the management of people with urinary incontinence who cannot participate in independent toileting. For this reason, it is commonly assumed to represent current practice in residential aged care settings.
Objectives
To assess the effects of timed voiding for the management of urinary incontinence in adults who cannot participate in independent toileting.
Search strategy
We searched the Cochrane Incontinence Group Specialised Register (28 February 2007), MEDLINE (January 1966 to November 2003), EMBASE (January 1980 to Week 18 2002), CINAHL (January 1982 to February 2001), PsycINFO (January 1972 to August 2002), Biological Abstracts (January 1980 to December 2000), Current Contents (January 1993 to December 2001) and the reference lists of relevant articles. We also contacted experts in the field, searched relevant websites and hand searched journals and conference proceedings.
Selection criteria
We selected all randomised and quasi-randomised trials that addressed timed voiding in an adult population and that had an alteration in continence status as a primary outcome. We included those trials that had assessed timed voiding delivered either alone or in combination with another intervention and compared it with either usual care, or no timed voiding, or another intervention.
Data collection and analysis
Data extraction and quality assessment were undertaken by at least two people working independently of each other. Any differences were resolved by discussion until agreement was reached. The relative risk for dichotomous data were calculated with 95% confidence intervals. Where data were insufficient to support a quantitative analysis, a narrative overview was undertaken.
Main results
Two trials with a total of 298 participants met the inclusion criteria. Both compared timed voiding plus additional intervention with usual care. In one of these timed voiding was combined with continence products, placement of a bedside commode for each participant, education to staff on transfer techniques, feedback and encouragement to staff, praise to participants for "successful responses" and administration of oxybutynin in small doses. The mean percentage who were incontinent when checked daily was 20% in the intervention group compared with 80% in the control group. No further between group analysis was possible from the data reported. The other trial combined timed voiding with a medical assessment and individualised medical management that was based on clinical data. Reduction in the number of participants with daytime and night-time incontinence was greater in the intervention group but this difference was statistically significant only for night-time wetting. There was no difference in the volume of urine lost as determined by pad weighing.
The methodological quality of these trials was not high based on the quality appraisal criteria of the Cochrane Incontinence Group. In particular, there was a lack of clarity regarding levels of blinding. It was not possible to combine data from trials. In both trials, the fixed schedule of toileting was combined with other interventions. The extent to which the results reflect the contribution of timed voiding is unknown because the trials' design did not allow assessment of the effects of the fixed schedule of toileting separately from other components of the interventions.
Authors' conclusions
The data were too few and of insufficient quality to provide empirical support for or against the intervention of timed voiding.