Estimating Prey Preference by Predators: Uses of Various Indices, and a Proposal of Another Based on χ2

1982 ◽  
Vol 39 (6) ◽  
pp. 914-923 ◽  
Author(s):  
Sifford Pearre Jr.
Keyword(s):  
Sample Size ◽  
Contingency Table ◽  
Prey Selection ◽  
Selection Index ◽  
Prey Preference ◽  
Chi Square ◽  
Exact Test ◽  
Biological Statistics

A really useful prey-selection index should be statistically testable. A 2 × 2 contingency table formulation provides a simple way to test the significance of any degree of selection at any sample size. An index ranging from −1 to +1, and zero-valued for no selection, can be simply derived from the chi-square formulation. Some conflicting usages in biological statistics texts are discussed, as well as the usefulness and limitations of other commonly used indices.Key words: selection, index, chi-square, exact test, prey

scholarly journals CYTOCHROME P450 CYP1B1*2 GENE AND ITS ASSOCIATION WITH T2D IN TABUK POPULATION, NORTHWESTERN REGION OF SAUDI ARABIA

2018 ◽  
Vol 11 (1) ◽  
pp. 55
Author(s):  
Imadeldin Elfaki ◽  
Fahad M Almutairi ◽  
Rashid Mir ◽  
Roaid Khan ◽  
Faisel Abu-duhier
Keyword(s):  
Cytochrome P450 ◽  
Sample Size ◽  
Cross Sectional Study ◽  
Fisher Exact Test ◽  
Large Sample Size ◽  
Genotype Distribution ◽  
Chi Square ◽  
Cross Sectional ◽  
Exact Test ◽  
Northwestern Region

Objective: Cytochrome P450 1B1 (CYP1B1) is involved in the activation of procarcinogens and steroid metabolism. Genetic variants of CYP1B1are associated with altered catalytic activity and disease phenotypes. The purpose of this study was to investigate the role of CYP1B1 (rs1056827) polymorphism in inducing T2D.Methods: This cross-sectional study enrolled 113 subjects of T2D and 120 controls. DNA was isolated from blood. Genotyping of the rs1056827 wasdone by allele-specific polymerase chain reaction. The frequency of alleles and genotype distribution was compared in T2D cases and healthy controls.Statistical analysis was performed with SPSS, Chi-square, and Fisher exact test. Hardy-Weinberg equilibrium was tested by a χ2 test. The associations between rs1056827 variant genotypes and T2D were estimated by computing the odds ratios and their 95% confidence intervals (CI) from univariate and multivariate logistic regression analysis.Results: A significant association of rs1056827 was found between T2D cases and controls (p<0.0001). When GG genotype was compared with GT genotype a significant association was found with odd ration (OD)0.24 (95% CI: (0.131–0.452) and risk ratio (RR) 0.45 (0.30–0.67) times the risk of T2D heterozygous with the G/T allele (p≤0.0002). In a comparison of GG homozygous with the TT homozygous, there was no significant association with the OD 0.38 (95% CI: (0.02–6.51) RR 0.55(0.13–2.35), p<0.49. When G allele was compared with the T allele a highly significant association with OD 0.54 (95% [CI]: (0.37–0.80) RR 0.75(0.630–0.897) < p≤0.003 suggesting a possible dominant effect of this polymorphism on T2D risk.Conclusion: This result suggests a significant association between rs1056827G>T polymorphism and T2D. This finding is limited due to the smaller sample size and can be validated by large sample size studies.

An Evaluation of Power and Sample-Size Requirements for the Continuity-Corrected Fisher Exact Test

1982 ◽  
Vol 54 (1) ◽  
pp. 83-86 ◽  
Author(s):  
John E. Overall ◽  
Chris W. Hornick
Keyword(s):  
Sample Size ◽  
Type I Error ◽  
Fisher Exact Test ◽  
Type I ◽  
Chi Square ◽  
Exact Test ◽  
Error Probabilities

This article evaluates power and Type I error probabilities for a modified Fisher exact test for homogeneity of response probabilities in 2 × 2 tables. The original Fisher exact test and the Pearson chi-square are employed as standards for comparison. The continuity-corrected Fisher statistic is shown to be considerably more powerful than the uncorrected Fisher exact test, while it is less often nonconservatively biased than the Pearson chi-square.

Impact of the p-Value Threshold on Interpretation of Trial Outcomes in Obstetrics and Gynecology

2021 ◽  
Author(s):  
Ann M. Bruno ◽  
Ashley E. Shea ◽  
Brett D. Einerson ◽  
Torri D. Metz ◽  
Amanda A. Allshouse ◽  
...  
Keyword(s):  
Sample Size ◽  
Primary Outcome ◽  
A Priori ◽  
Sample Size Calculation ◽  
P Value ◽  
Chi Square ◽  
Level Of Evidence ◽  
Exact Test ◽  
Manual Search ◽  
Significance Threshold

Objective Randomized controlled trials (RCTs) are considered the highest level of evidence to inform clinical practice. However, the reproducibility crisis has raised concerns about the scientific rigor of published RCT findings. Some advocate for a lower p-value threshold. We aimed to review published OB/Gyn topical RCTs in three representative OB/Gyn journals and three high impact non-OB/Gyn journals to determine if their interpretations would change with adoption of a p-value threshold for significance of 0.005. Secondarily, we evaluated if there were differences in methodologic characteristics between those that did and did not lose significance. Study Design A manual search was performed to identify all OB/Gyn RCTs published in the selected journals between July 2017 and June 2019. Data were collected on primary outcome(s), methodology, and p-values. We determined the proportion of primary outcomes that would remain statistically significant with adoption of a p-value significance threshold of 0.005 versus be reinterpreted as “suggestive” (defined as p-value between 0.005 and 0.05). Chi-square or Fisher's exact test were used to compare study characteristics. Results Overall, 202 RCTs met inclusion criteria; 52% in obstetrics and 48% in gynecology. Of 90 studies considered significant with p <0.05 at the time of publication, 54.4% (n = 49) would maintain significant (p < 0.005), while 45.6% (n = 41) would become suggestive using the lower threshold. Most RCTs utilized a single (90.1%) versus composite (8.9%) primary outcome type, used an intent-to-treat analysis (73.3%), and studied a drug intervention (46.5%). Methodologically, 23.7% did not prespecify analysis type, 28.2% did not meet the pre-determined sample size, and 9.4% did not report an a priori sample size calculation. Studies maintaining significance were more likely to be international and report a funding source. Conclusion Adopting a p-value significance threshold of 0.005 would require reinterpretation of almost half of RCT results in the OB/Gyn literature. Highly variable methodological quality was identified. Key Points

scholarly journals CYTOCHROME P450 CYP1B1*2 GENE AND ITS ASSOCIATION WITH T2D IN TABUK POPULATION, NORTHWESTERN REGION OF SAUDI ARABIA

2018 ◽  
Vol 11 (1) ◽  
pp. 55 ◽  
Author(s):  
Imadeldin Elfaki ◽  
Fahad M Almutairi ◽  
Rashid Mir ◽  
Roaid Khan ◽  
Faisel Abu-duhier
Keyword(s):  
Cytochrome P450 ◽  
Sample Size ◽  
Cross Sectional Study ◽  
Fisher Exact Test ◽  
Large Sample Size ◽  
Genotype Distribution ◽  
Chi Square ◽  
Cross Sectional ◽  
Exact Test ◽  
Northwestern Region

Objective: Cytochrome P450 1B1 (CYP1B1) is involved in the activation of procarcinogens and steroid metabolism. Genetic variants of CYP1B1are associated with altered catalytic activity and disease phenotypes. The purpose of this study was to investigate the role of CYP1B1 (rs1056827) polymorphism in inducing T2D.Methods: This cross-sectional study enrolled 113 subjects of T2D and 120 controls. DNA was isolated from blood. Genotyping of the rs1056827 wasdone by allele-specific polymerase chain reaction. The frequency of alleles and genotype distribution was compared in T2D cases and healthy controls.Statistical analysis was performed with SPSS, Chi-square, and Fisher exact test. Hardy-Weinberg equilibrium was tested by a χ2 test. The associations between rs1056827 variant genotypes and T2D were estimated by computing the odds ratios and their 95% confidence intervals (CI) from univariate and multivariate logistic regression analysis.Results: A significant association of rs1056827 was found between T2D cases and controls (p<0.0001). When GG genotype was compared with GT genotype a significant association was found with odd ration (OD)0.24 (95% CI: (0.131–0.452) and risk ratio (RR) 0.45 (0.30–0.67) times the risk of T2D heterozygous with the G/T allele (p≤0.0002). In a comparison of GG homozygous with the TT homozygous, there was no significant association with the OD 0.38 (95% CI: (0.02–6.51) RR 0.55(0.13–2.35), p<0.49. When G allele was compared with the T allele a highly significant association with OD 0.54 (95% [CI]: (0.37–0.80) RR 0.75(0.630–0.897) < p≤0.003 suggesting a possible dominant effect of this polymorphism on T2D risk.Conclusion: This result suggests a significant association between rs1056827G>T polymorphism and T2D. This finding is limited due to the smaller sample size and can be validated by large sample size studies.

Venous Thromboembolism and High Grade Gliomas

1993 ◽  
Vol 70 (03) ◽  
pp. 393-396 ◽  
Author(s):  
Mandeep S Dhami ◽  
Robert D Bona ◽  
John A Calogero ◽  
Richard M Hellman
Keyword(s):  
Risk Factors ◽  
Venous Thromboembolism ◽  
Medical Center ◽  
Significant Risk ◽  
Bleeding Complications ◽  
Fisher Exact Test ◽  
High Grade ◽  
Chi Square ◽  
Exact Test ◽  
High Grade Gliomas

SummaryA retrospective study was done to determine the incidence of and the risk factors predisposing to clinical venous thromboembolism (VTE) in patients treated for high grade gliomas. Medical records of 68 consecutive patients diagnosed and treated at Saint Francis Hospital and Medical Center from January 1986 to June 1991 were reviewed. The follow up was to time of death or at least 6 months (up to December 1991). All clinically suspected episodes of VTE were confirmed by objective tests. Sixteen episodes of VTE were detected in 13 patients for an overall episode rate of 23.5%. Administration of chemotherapy (p = 0.027, two tailed Fisher exact test) and presence of paresis (p = 0.031, two tailed Fisher exact test) were statistically significant risk factors for the development of VTE. Thrombotic events were more likely to occur in the paretic limb and this difference was statistically significant (p = 0.00049, chi square test, with Yates correction). No major bleeding complications were seen in the nine episodes treated with long term anticoagulation.We conclude that venous thromboembolic complications are frequently encountered in patients being treated for high grade gliomas and the presence of paresis and the administration of chemotherapy increases the risk of such complications.

Use of SAMe-TT₂R₂ Score to Predict the Quality of Anticoagulation Control in Patients with Atrial Fibrillation Receiving Warfarin in Thailand

2020 ◽  
Vol 103 (6) ◽  
pp. 548-552
Keyword(s):  
Atrial Fibrillation ◽  
Therapeutic Range ◽  
Statistical Significance ◽  
Discrimination Performance ◽  
Poor Quality ◽  
Chi Square ◽  
Exact Test ◽  
Time In Therapeutic Range ◽  
Anticoagulation Control

Objective: To predict the quality of anticoagulation control in patients with atrial fibrillation (AF) receiving warfarin in Thailand. Materials and Methods: The present study retrospectively recruited Thai AF patients receiving warfarin for three months or longer between June 2012 and December 2017 in Central Chest Institute of Thailand. The patients were classified into those with SAMe-TT₂R₂ of 2 or less, and 3 or more. The Chi-square test or Fisher’s exact test was used to compare the proportion of the patients with poor time in therapeutic range (TTR) between the two groups of SAMe-TT₂R₂ score. The discrimination performance of SAMe-TT₂R₂ score was demonstrated with c-statistics. Results: Ninety AF patients were enrolled. An average age was 69.89±10.04 years. Most patients were persistent AF. An average CHA₂DS₂-VASc, SAMe-TT₂R₂, and HAS-BLED score were 3.68±1.51, 3.26±0.88, and 1.98±0.85, respectively. The present study showed the increased proportion of AF patients with poor TTR with higher SAMe-TT₂R₂ score. The AF patients with SAMe-TT₂R₂ score of 3 or more had a larger proportion of patients with poor TTR than those with SAMe-TT₂R₂ score of 2 or less with statistical significance when TTR was below 70% (p=0.03) and 65% (p=0.04), respectively. The discrimination performance of SAMe-TT₂R₂ score was demonstrated with c-statistics of 0.60, 0.59, and 0.55 when TTR was below 70%, 65% and 60%, respectively. Conclusion: Thai AF patients receiving warfarin had a larger proportion of patients with poor TTR when the SAMe-TT₂R₂ score was higher. The score of 3 or more could predict poor quality of anticoagulation control in those patients. Keywords: Time in therapeutic range, Poor quality of anticoagulation control, Warfarin, SAMe-TT₂R₂, Labile INR

PREEMPTIVE ANALGESIA WITH AMITRIPTYLINE IN WOMEN UNDERGOING ABDOMINAL HYSTERECTOMY: A RANDOMIZED CLINICAL TRIAL

2020 ◽  
pp. 2-5
Author(s):  
Antônio Henriques De França Neto ◽  
Alexandre Magno Nóbrega Marinho ◽  
Eveline Pereira De Arruda Agra ◽  
Priscilla Guimarães Alves ◽  
Josikwylkson Costa Brito ◽  
...  
Keyword(s):  
Clinical Trial ◽  
Postoperative Pain ◽  
Pressure Pain Threshold ◽  
Abdominal Hysterectomy ◽  
Tricyclic Antidepressant ◽  
Preemptive Analgesia ◽  
Chi Square ◽  
Double Blind ◽  
Exact Test ◽  
Student’S T

The concept of preemptive analgesia, albeit long-standing, has reemerged. Consequently, recent research has focused on testing a variety of drugs preoperatively to prevent the occurrence of postoperative pain, a major factor of morbidity. Amitriptyline is a tricyclic antidepressant used to treat chronic pain. Because amitriptyline acts on pain transmission pathways, it could theoretically be used as an agent for the prevention of postoperative pain. This study evaluated the effectiveness of amitriptyline in preventing pain in patients submitted to hysterectomy, the most commonly performed gynecological surgery. A randomized, double-blind clinical trial was conducted with 145 patients, 72 of these receiving amitriptyline and 73 placebo. All patients were evaluated at 6, 12, 24 and 48 hours after surgery using a visual analog scale (VAS) for pain and algometry to determine the pressure-pain threshold. Statistical analysis was conducted using the chi-square test of association, Student's t-test, and the Mann-Whitney test, with Fisher's exact test being used whenever appropriate. No statistically signicant difference was found between the two groups with respect to pain at any of the time points evaluated, leading to the conclusion that at a dose of 25 mg, amitriptyline is ineffective in preventing postoperative pain in patients submitted to abdominal hysterectomy

Success Rate of Obturation of Root Canals by Different Techniques in Primary Molars: A Comparative Clinical Study

2020 ◽  
Vol 2 (1) ◽  
pp. 36-44
Author(s):  
Satyawan G. Damle ◽  
Ritika Bansal ◽  
Dhanashree D. Sakhare
Keyword(s):  
Success Rate ◽  
Study Groups ◽  
Primary Molars ◽  
Control Group ◽  
Second Primary ◽  
Chi Square ◽  
Exact Test ◽  
Root Canals ◽  
Significant Difference ◽  
Comparative Clinical Study

Objective: To compare the success rate of different obturation procedures in primary mandibular second molars clinically and also by digital radiovisiography. Methods: A total of 40 children aged between 4-8 years with deeply carious mandibular second primary molars indicated for single session pulpectomy were selected. Canals were obturated with Metapex. The 3 study groups (Endodontic plugger, Handheld lentulospiral, Navi Tip syringe) were compared with the control group (reamer) both clinically and radiovisiographically. The data collected were statistically analyzed using Pearson’s Chi-square and Fisher’s exact test. Results: The use of Navi tip syringe led to the least number of voids followed by Endodontic plugger and Reamer and the highest number of voids was reported with Lentulospiral. Navitip presented maximum number of optimally filled cases followed by Endodontic plugger and Lentulospiral and least number of optimally filled cases with reamer. However, there was no statistically significant difference (p>0.05) in any of the groups with clinical (pain and tenderness to percussion) and radiographic parameters (presence or absence of voids and length of obturation). Conclusion: Within the limitations of the present study, though the clinical outcome was statistically insignificant, Navitip syringe exhibited encouraging results and is a promising option for obturation in primary teeth.

scholarly journals Optimal breeding-value prediction using a Sparse Selection Index

Genetics ◽  
2021 ◽  
Author(s):  
Marco Lopez-Cruz ◽  
Gustavo de los Campos
Keyword(s):  
Sample Size ◽  
Dna Sequences ◽  
Genomic Prediction ◽  
Prediction Accuracy ◽  
Regularization Parameter ◽  
Selection Index ◽  
Prediction Method ◽  
Training Data ◽  
Breeding Value ◽  
Data Set

Abstract Genomic prediction uses DNA sequences and phenotypes to predict genetic values. In homogeneous populations, theory indicates that the accuracy of genomic prediction increases with sample size. However, differences in allele frequencies and in linkage disequilibrium patterns can lead to heterogeneity in SNP effects. In this context, calibrating genomic predictions using a large, potentially heterogeneous, training data set may not lead to optimal prediction accuracy. Some studies tried to address this sample size/homogeneity trade-off using training set optimization algorithms; however, this approach assumes that a single training data set is optimum for all individuals in the prediction set. Here, we propose an approach that identifies, for each individual in the prediction set, a subset from the training data (i.e., a set of support points) from which predictions are derived. The methodology that we propose is a Sparse Selection Index (SSI) that integrates Selection Index methodology with sparsity-inducing techniques commonly used for high-dimensional regression. The sparsity of the resulting index is controlled by a regularization parameter (λ); the G-BLUP (the prediction method most commonly used in plant and animal breeding) appears as a special case which happens when λ = 0. In this study, we present the methodology and demonstrate (using two wheat data sets with phenotypes collected in ten different environments) that the SSI can achieve significant (anywhere between 5-10%) gains in prediction accuracy relative to the G-BLUP.

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