scholarly journals 208 Do prediction equations with high R-squared in low sample size studies have high predictive ability?

2020 ◽  
Vol 98 (Supplement_3) ◽  
pp. 71-71
Author(s):  
Nick Serão ◽  
Amy Petry
Keyword(s):  
Rank Correlation ◽  
Predictive Ability ◽  
Prediction Equation ◽  
Small Sample ◽  
P Value ◽  
Prediction Equations ◽  
Nursery Pigs ◽  
Linear Effect ◽  
Randomized Design ◽  
Small Sample Sizes

Abstract The use of R-squared as a measurement of prediction in regression is a common practice in animal nutrition studies. Generally, studies use data used to estimate the prediction equation to calculate the R-squared of the equation, which does not represent prediction. The objective was to evaluate the predictive ability of prediction equations using independent datasets. Data were simulated in based on previously reported prediction equations for ADG in nursery pigs: 152 + 195(SID_Lysine%). A completely randomized design with SID_Lysine% levels of 1.2, 1.3, and 1.4% was used. Data were simulated for three CVs representing low, moderate, and high variation in ADG, for low number of replicates per treatment (RepTreat; 4 to 10, every 2). Data were simulated and analyses performed 300 times for each scenario. Prediction equations were estimated for each scenario when significant effect of SID_Lysine% was followed by a significant orthogonal contrast testing the linear effect of SID_Lysine% (P-value< 0.05), and their R-squared were calculated (R2_training). The prediction equation was used to test the fit of the other datasets, and their R-squared were calculated and averaged for each prediction equation (R2_prediction). The relationship between R2_training and R2_prediction was assessed through Spearmen’s correlation and regression of R2_prediction on R2_training, across scenarios. The R2_training and R2_prediction averages were similar with 94.5% and 93.9%, 66.0% and 63.5%, and 46.1% and 42.7%, for low, moderate, and high CVs, respectively. The rank-correlation between R2_training and R2_prediction increased with CV: 0.23, 0.67, and 0.77, for low, moderate, and high CV, respectively. From regression analysis of R2_prediction on R2_training, as CV increased bias increased, with prediction equations with greater R2_training overestimating R2_prediction, and prediction equations with lower R2_training underestimating R2_prediction. These results indicate that in small sample sizes (≤10 per treatment), as CV increases, models with high R-squared are overestimated, and are not as predictable.

scholarly journals O6B.4 Laryngeal cancer risks in workers exposed to lung carcinogens: exposure-effect analyses using a quantitative job exposure matrix

2019 ◽  
Vol 76 (Suppl 1) ◽  
pp. A54.1-A54
Author(s):  
Amy Hall ◽  
Hans Kromhout ◽  
Joachim Schüz ◽  
Lützen Portengen ◽  
Susan Peters ◽  
...  
Keyword(s):  
Latin American ◽  
Laryngeal Cancer ◽  
Small Sample ◽  
P Value ◽  
Lung Cancers ◽  
Logistic Regression Models ◽  
Exposure Effect ◽  
Blue Collar Workers ◽  
Chromium Vi ◽  
Small Sample Sizes

BackgroundVarious occupational agents are suspected risk factors for laryngeal cancer. However, individual studies are often inadequate to investigate how such exposures relate to this relatively rare outcome. Important limitations include small sample sizes, lack of detail on exposure, and inadequate adjustment for confounders.MethodsThis study applied quantitative estimates via SYN-JEM for four established occupational lung carcinogens to case-control data from five (Western European and Latin American) studies within the International Head and Neck Cancer Epidemiology Consortium. Participant job histories for n=2256 laryngeal cancer cases and n=7857 controls recruited from 1989–2007 were linked with quantitative SYN-JEM estimates via ISCO-68 codes. Logistic regression models were applied to assess the effects of occupational exposure to asbestos, respirable crystalline silica (RCS), chromium-VI, and nickel on laryngeal cancer risk while controlling for tobacco and alcohol consumption.ResultsIncreased ORs were observed for all agents evaluated. In males, a positive exposure-effect relationship was observed with duration of RCS exposure (p-value for trend <0.01). Relatively strong effects were also observed in the highest categories of career-cumulative chromium-VI exposure (>90%ile: OR=2.21, 95% CI=1.13–4.33) and career-average exposure (>90%ile: OR=2.96, 95% CI=1.51–5.79), and in the highest category of career-cumulative nickel/chromium-VI combined exposure (>90%ile: OR=1.51, 95% CI=1.01–2.26). These relationships weakened in analyses restricted to blue collar workers but interpretations remained unchanged.ConclusionsThese results support causal links between exposure to known lung carcinogens and laryngeal cancer. Measures to reduce such exposures in workplaces could decrease the risk of both laryngeal and lung cancers.

Integrating Visual and Bayesian Statistical Analyses in Single Case Experimental Research to Evaluate the Effectiveness and Magnitude of a Comprehensive Behavioral Intervention

2018 ◽  
Author(s):  
Prathiba Natesan ◽  
Smita Mehta
Keyword(s):  
Behavioral Intervention ◽  
Effect Size ◽  
Rate Ratio ◽  
Visual Analysis ◽  
Single Case ◽  
Small Sample ◽  
Statistical Analyses ◽  
Data Types ◽  
Ratio Effect ◽  
Small Sample Sizes

Single case experimental designs (SCEDs) have become an indispensable methodology where randomized control trials may be impossible or even inappropriate. However, the nature of SCED data presents challenges for both visual and statistical analyses. Small sample sizes, autocorrelations, data types, and design types render many parametric statistical analyses and maximum likelihood approaches ineffective. The presence of autocorrelation decreases interrater reliability in visual analysis. The purpose of the present study is to demonstrate a newly developed model called the Bayesian unknown change-point (BUCP) model which overcomes all the above-mentioned data analytic challenges. This is the first study to formulate and demonstrate rate ratio effect size for autocorrelated data, which has remained an open question in SCED research until now. This expository study also compares and contrasts the results from BUCP model with visual analysis, and rate ratio effect size with nonoverlap of all pairs (NAP) effect size. Data from a comprehensive behavioral intervention are used for the demonstration.

No Evidence that Experiencing Physical Warmth Promotes Interpersonal Warmth: Two Failures to Replicate Williams and Bargh (2008)

2018 ◽  
Author(s):  
Christopher Chabris ◽  
Patrick Ryan Heck ◽  
Jaclyn Mandart ◽  
Daniel Jacob Benjamin ◽  
Daniel J. Simons
Keyword(s):  
Null Hypothesis ◽  
Small Sample ◽  
Sample Sizes ◽  
Double Blind ◽  
Bayesian Analyses ◽  
Physical Warmth ◽  
Small Sample Sizes ◽  
Interpersonal Warmth

Williams and Bargh (2008) reported that holding a hot cup of coffee caused participants to judge a person’s personality as warmer, and that holding a therapeutic heat pad caused participants to choose rewards for other people rather than for themselves. These experiments featured large effects (r = .28 and .31), small sample sizes (41 and 53 participants), and barely statistically significant results. We attempted to replicate both experiments in field settings with more than triple the sample sizes (128 and 177) and double-blind procedures, but found near-zero effects (r = –.03 and .02). In both cases, Bayesian analyses suggest there is substantially more evidence for the null hypothesis of no effect than for the original physical warmth priming hypothesis.

scholarly journals Performance, gut morphometry and enzymatic activity of broilers fed neonatal supplementation in housing

2018 ◽  
Vol 40 (1) ◽  
pp. 38423
Author(s):  
Tatiane Souza dos Santos ◽  
Adriano Barbieri ◽  
Robert Guaracy Aparecido Cardoso Araujo ◽  
Gustavo Do Valle Polycarpo ◽  
Daniela Felipe Pinheiro ◽  
...  
Keyword(s):  
Amino Acids ◽  
Polynomial Regression ◽  
Pancreatic Enzyme ◽  
Broiler Chicks ◽  
Quadratic Effect ◽  
Linear Effect ◽  
Intestinal Length ◽  
Randomized Design ◽  
Relative Organ Weight ◽  
Completely Randomized Design

The objective was to evaluate the performance, relative organ weight, morphometry, intestinal length and pancreatic enzyme activity of broilers receiving neonatal supplementation. A total of 900 Cobb 500 broiler chicks was housed in 30 boxes of 2.5 m². The treatments were divided in a completely randomized design with six replications, and consisted of five inclusion levels (0.0, 2.5, 5.0, 7.5 and 10 grams per bird). The supplement used was based of amino acids, vitamins and minerals, which was provided on the ration on the first day in the housing. Statistical analysis was performed using SAS (2008) and when significant broken down using a polynomial regression. Due to the inclusion of the neonatal supplement in the period from one to seven and one to 21 days of age, the feed intake presented a linear effect and the weight gain, a quadratic effect. The relative weights of the gizzard and liver showed a quadratic effect, and the inclusions of 4.18 and 3.41 grams/bird provided the lowest weights, respectively. The jejunum villi height decreased with supplementation as well as the activity of pancreatic lipase. It can be concluded that neonatal supplementation benefited the performance of birds up to 21 days of age.

scholarly journals Non-Invasive Monitoring of Adrenocortical Activity in Three Sympatric Desert Gerbil Species

Animals ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 75
Author(s):  
Álvaro Navarro-Castilla ◽  
Mario Garrido ◽  
Hadas Hawlena ◽  
Isabel Barja
Keyword(s):  
Small Sample ◽  
Post Injection ◽  
Control Groups ◽  
Treatment Groups ◽  
Adrenocortical Activity ◽  
Non Invasive ◽  
Endocrine Status ◽  
Corticosterone Metabolites ◽  
Small Sample Sizes ◽  
Fecal Corticosterone Metabolites

The study of the endocrine status can be useful to understand wildlife responses to the changing environment. Here, we validated an enzyme immunoassay (EIA) to non-invasively monitor adrenocortical activity by measuring fecal corticosterone metabolites (FCM) in three sympatric gerbil species (Gerbillus andersoni, G. gerbillus and G. pyramidum) from the Northwestern Negev Desert’s sands (Israel). Animals included into treatment groups were injected with adrenocorticotropic hormone (ACTH) to stimulate adrenocortical activity, while control groups received a saline solution. Feces were collected at different intervals and FCM were quantified by an EIA. Basal FCM levels were similar in the three species. The ACTH effect was evidenced, but the time of FCM peak concentrations appearance differed between the species (6–24 h post-injection). Furthermore, FCM peak values were observed sooner in G. andersoni females than in males (6 h and 18 h post-injection, respectively). G. andersoni and G. gerbillus males in control groups also increased FCM levels (18 h and 48 h post-injection, respectively). Despite the small sample sizes, our results confirmed the EIA suitability for analyzing FCM in these species as a reliable indicator of the adrenocortical activity. This study also revealed that close species, and individuals within a species, can respond differently to the same stressor.

scholarly journals PSV-8 Glucocorticoid receptor agonist (GRA): what is the best delivery method to newly weaned pigs?

2020 ◽  
Vol 98 (Supplement_3) ◽  
pp. 158-159
Author(s):  
Hailey Wooten ◽  
Hwanhee Kim ◽  
Amanda Rakhshandeh ◽  
Anoosh Rakhshandeh
Keyword(s):  
Growth Performance ◽  
Performance Outcomes ◽  
Nutrient Digestibility ◽  
Control Group ◽  
Free Access ◽  
Weaned Pigs ◽  
Delivery Methods ◽  
Nursery Pigs ◽  
Intestinal Integrity ◽  
Randomized Design

Abstract We previously found that i.m. injection of GRA, similar to in-feed antibiotics, improves measures of intestinal integrity, nutrient digestibility, and overall growth performance in nursery pigs. In addition, we have demonstrated that the mitigating effects of GRA on the stress of weaning is predominantly done by subsiding the inflammatory response that often accompanies early weaning. The objective of the current study was to explore the most practical methods for delivering GRA to newly weaned pigs. One-hundred and sixty-seven PIC pigs were weaned at 25 ±1.0 days of age (BW 7 ±1.2 kg), and assigned to fourteen treatments (3-4 pigs /pen; 3 pens/treatment). Seven treatments were tested within two sexes (gilts vs. barrows). The treatments were: 1) i.m. injection of GRA (two injections, 0.2 mg/kg BW at -1 and 3 d post-weaning), 2) two levels of in-water GRA (0.8 and 1.6 ppm), 3) in-feed GRA (2.5 and 5.0 ppm), 4) in-feed antibiotic (ANT, 100 ppm tylosin), and 5) control. Dexamethasone was used as GRA. Pigs had free access to in-feed or in-water GRA or ANT during the 1st-week post-weaning. Parameters of growth performance were measured weekly until the end of the nursery phase. A completely randomized design and repeated measurement ANOVA (PROC MIXED) in SAS were used for statistical analyses. In-water, in-feed, and i.m. GRA treatments resulted in growth performance outcomes comparable to that of in-feed ANT. Relative to CON pigs, both ANT and GRA improved ADG and G: F during the nursery phase (P &lt; 0.05). Among the delivery methods tested, 2.5 ppm of in-feed GRA resulted in superior ADG (GRA vs. CON; 0.29 vs. 0.20 kg/d) and G: F (0.63 vs. 0.40 ± 0.05), compared to the control group (P &lt; 0.02). Collectively, these results suggested that in-feed treatment is the best method for delivering GRA to newly weaned pigs.

scholarly journals Use of Antiplatelet Agents Decreases the Positive Predictive Value of Fecal Immunochemical Tests for Colorectal Cancer but Does Not Affect Their Sensitivity

2021 ◽  
Vol 11 (6) ◽  
pp. 497
Author(s):  
Yoonsuk Jung ◽  
Eui Im ◽  
Jinhee Lee ◽  
Hyeah Lee ◽  
Changmo Moon
Keyword(s):  
Colorectal Cancer ◽  
Large Scale ◽  
Screening Program ◽  
Antiplatelet Agents ◽  
Population Based ◽  
Small Sample ◽  
Antithrombotic Agents ◽  
Predictive Values ◽  
Prescription Rates ◽  
Small Sample Sizes

Previous studies have evaluated the effects of antithrombotic agents on the performance of fecal immunochemical tests (FITs) for the detection of colorectal cancer (CRC), but the results were inconsistent and based on small sample sizes. We studied this topic using a large-scale population-based database. Using the Korean National Cancer Screening Program Database, we compared the performance of FITs for CRC detection between users and non-users of antiplatelet agents and warfarin. Non-users were matched according to age and sex. Among 5,426,469 eligible participants, 768,733 used antiplatelet agents (mono/dual/triple therapy, n = 701,683/63,211/3839), and 19,569 used warfarin, while 4,638,167 were non-users. Among antiplatelet agents, aspirin, clopidogrel, and cilostazol ranked first, second, and third, respectively, in terms of prescription rates. Users of antiplatelet agents (3.62% vs. 4.45%; relative risk (RR): 0.83; 95% confidence interval (CI): 0.78–0.88), aspirin (3.66% vs. 4.13%; RR: 0.90; 95% CI: 0.83–0.97), and clopidogrel (3.48% vs. 4.88%; RR: 0.72; 95% CI: 0.61–0.86) had lower positive predictive values (PPVs) for CRC detection than non-users. However, there were no significant differences in PPV between cilostazol vs. non-users and warfarin users vs. non-users. For PPV, the RR (users vs. non-users) for antiplatelet monotherapy was 0.86, while the RRs for dual and triple antiplatelet therapies (excluding cilostazol) were 0.67 and 0.22, respectively. For all antithrombotic agents, the sensitivity for CRC detection was not different between users and non-users. Use of antiplatelet agents, except cilostazol, may increase the false positives without improving the sensitivity of FITs for CRC detection.

scholarly journals Perioperative digital behaviour change interventions for reducing alcohol consumption, improving dietary intake, increasing physical activity and smoking cessation: a scoping review

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
Katarina Åsberg ◽  
Marcus Bendtsen
Keyword(s):  
Physical Activity ◽  
Smoking Cessation ◽  
Behaviour Change ◽  
Scoping Review ◽  
Text Messaging ◽  
Text Message ◽  
Feasibility Studies ◽  
Small Sample ◽  
Small Sample Sizes ◽  
Randomised Controlled

Abstract Background Evidence suggests that unhealthy lifestyle behaviours are modifiable risk factors for postoperative complications. Digital behaviour change interventions (DBCIs), for instance text messaging programs and smartphone apps, have shown promise in achieving lifestyle behaviour change in a wide range of clinical populations, and it may therefore be possible to reduce postoperative complications by supporting behaviour change perioperatively using digital interventions. This scoping review was conducted in order to identify existing research done in the area of perioperative DBCIs for reducing alcohol consumption, improving dietary intake, increasing physical activity and smoking cessation. Main text This scoping review included eleven studies covering a range of surgeries: bariatric, orthopaedic, cancer, transplantation and elective surgery. The studies were both randomised controlled trials and feasibility studies and investigated a diverse set of interventions: one game, three smartphone apps, one web-based program and five text message interventions. Feasibility studies reported user acceptability and satisfaction with the behaviour change support. Engagement data showed participation rates ranged from 40 to 90%, with more participants being actively engaged early in the intervention period. In conclusion, the only full-scale randomised controlled trial (RCT), text messaging ahead of bariatric surgery did not reveal any benefits with respect to adherence to preoperative exercise advice when compared to a control group. Two of the pilot studies, one text message intervention, one game, indicated change in a positive direction with respect to alcohol and tobacco outcomes, but between group comparisons were not done due to small sample sizes. The third pilot-study, a smartphone app, found between group changes for physical activity and alcohol, but not with respect to smoking cessation outcomes. Conclusion This review found high participant satisfaction, but shows recruitment and timing-delivery issues, as well as low retention to interventions post-surgery. Small sample sizes and the use of a variety of feasibility outcome measures prevent the synthesis of results and makes generalisation difficult. Future research should focus on defining standardised outcome measures, enhancing patient engagement and improving adherence to behaviour change prior to scheduled surgery.

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