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Journal of Investigative Medicine : the... Oct 2016A threshold probability value of 'p≤0.05' is commonly used in clinical investigations to indicate statistical significance. To allow clinicians to better understand... (Review)
Review
A threshold probability value of 'p≤0.05' is commonly used in clinical investigations to indicate statistical significance. To allow clinicians to better understand evidence generated by research studies, this review defines the p value, summarizes the historical origins of the p value approach to hypothesis testing, describes various applications of p≤0.05 in the context of clinical research and discusses the emergence of p≤5×10(-8) and other values as thresholds for genomic statistical analyses. Corresponding issues include a conceptual approach of evaluating whether data do not conform to a null hypothesis (ie, no exposure-outcome association). Importantly, and in the historical context of when p≤0.05 was first proposed, the 1-in-20 chance of a false-positive inference (ie, falsely concluding the existence of an exposure-outcome association) was offered only as a suggestion. In current usage, however, p≤0.05 is often misunderstood as a rigid threshold, sometimes with a misguided 'win' (p≤0.05) or 'lose' (p>0.05) approach. Also, in contemporary genomic studies, a threshold of p≤10(-8) has been endorsed as a boundary for statistical significance when analyzing numerous genetic comparisons for each participant. A value of p≤0.05, or other thresholds, should not be employed reflexively to determine whether a clinical research investigation is trustworthy from a scientific perspective. Rather, and in parallel with conceptual issues of validity and generalizability, quantitative results should be interpreted using a combined assessment of strength of association, p values, CIs, and sample size.
Topics: Confidence Intervals; Genomics; Probability; Sample Size; Superstitions
PubMed: 27489256
DOI: 10.1136/jim-2016-000206 -
Perspectives on Medical Education 2024The use of the p-value in quantitative research, particularly its threshold of "P < 0.05" for determining "statistical significance," has long been a cornerstone of...
The use of the p-value in quantitative research, particularly its threshold of "P < 0.05" for determining "statistical significance," has long been a cornerstone of statistical analysis in research. However, this standard has been increasingly scrutinized for its potential to mislead findings, especially when the practical significance, the number of comparisons, or the suitability of statistical tests are not properly considered. In response to controversy around use of p-values, the American Statistical Association published a statement in 2016 that challenged the research community to abandon the term "statistically significant". This stance has been echoed by leading scientific journals to urge a significant reduction or complete elimination in the reliance on p-values when reporting results. To provide guidance to researchers in health professions education, this paper provides a succinct overview of the ongoing debate regarding the use of p-values and the definition of p-values. It reflects on the controversy by highlighting the common pitfalls associated with p-value interpretation and usage, such as misinterpretation, overemphasis, and false dichotomization between "significant" and "non-significant" results. This paper also outlines specific recommendations for the effective use of p-values in statistical reporting including the importance of reporting effect sizes, confidence intervals, the null hypothesis, and conducting sensitivity analyses for appropriate interpretation. These considerations aim to guide researchers toward a more nuanced and informative use of p-values.
Topics: Humans; Data Interpretation, Statistical; Research Design
PubMed: 38680196
DOI: 10.5334/pme.1324 -
Medical Hypothesis, Discovery &... 2023Proper correction of spherical aberration using intraocular lenses requires precise selection of the sphericity of intraocular lens surfaces based on individual...
BACKGROUND
Proper correction of spherical aberration using intraocular lenses requires precise selection of the sphericity of intraocular lens surfaces based on individual biometric data and corneal asphericity coefficient (Q value). This study aimed to determine and analyze the corneal Q value and its related factors among Saudi participants.
METHODS
In this cross-sectional study, normal right eyes of healthy Saudi participants aged 17 - 58 years who visited Al-Kahhal Medical Complex, Dammam, Saudi Arabia, were included. The Pentacam rotating Scheimpflug camera was used to determine the average Q value at 6-mm diameter. Q values were obtained from each quadrant (superior, nasal, inferior, and temporal) and two meridians (horizontal and vertical). Mean Q values of the anterior and posterior corneal surfaces were also obtained. Other factors including age, sex, refractive error, and central corneal radius were documented.
RESULTS
Five hundred right eyes from 500 participants were included. The mean (standard deviation [SD]) (range) age was 27.2 (7.1) (18 - 58) years. The mean (SD) (range) Q value of 500 eyes was - 0.24 (0.10) (- 0.71 to + 0.09) anteriorly and - 0.16 (0.14) (- 0.70 to + 0.23) posteriorly, being significantly more prolate anteriorly ( < 0.05). The corneas were significantly more prolate in the nasal than in the temporal quadrant, in the superior than in the inferior quadrant, and in the horizontal than in the vertical meridian (all < 0.05). There were statistically significant differences in anterior, nasal, temporal, inferior, horizontal, and vertical Q values among age groups (all < 0.05) but not in the superior or posterior Q values (both > 0.05). The corneas became less prolate with increasing age ( < 0.05). However, Q values were comparable between the sexes (all > 0.05). There was no significant correlation between anterior (r = + 0.08; = 0.095) or posterior (r = - 0.08; = 0.092) Q value and spherical equivalent, but a significant trend was detected toward more prolate shape with increasing myopia in the temporal and inferior quadrants (r = + 0.19; < 0.001, r = + 0.10; = 0.022, respectively). There was a significant negligible correlation between the posterior Q value and central corneal radius (r = - 0.18; < 0.001) but no significant correlation between the anterior Q value and central corneal radius (r = + 0.02; = 0.673).
CONCLUSIONS
Most corneas in this Saudi population were prolate in contour. Anterior corneal asphericity was positively correlated with age and was not significantly related to sex, refractive error, or central corneal radius. Further studies are needed to verify our preliminary findings.
PubMed: 38476574
DOI: 10.51329/mehdiophthal1479 -
Journal of Medical Biochemistry Aug 2023The aim was examination of the intimamedia thickness of carotid arteries in COVID-19 infection.
BACKGROUND
The aim was examination of the intimamedia thickness of carotid arteries in COVID-19 infection.
METHODS
In 50 patients, the thickness of the intimomedial complex (IMT) in the common carotid arteries was measured. The values were compared with the control group in 2006-9. The condition of the lungs was assessed by ultrasound score (It score) (0-42) as mild (0-14) or mediumsevere (15-28) Covid. IMT thickening risk factors and the value of fibrinogen, IL-6 and CRP were recorded. Two IMT prediction models were formed. The socio-epidemiological model predicts the development of IMT based on epidemiological factors. Apart from these factors, the second model also includes the values of the mentioned biomarkers.
RESULTS
It score 20±6, IMT values right: median 0.99 mm, p25=0.89, p75=1.14; left: 1±0.22 mm. Control: IMTright: median 0.7 mm, p25=0.68 mm; p75=0-9 mm; left: median=0.75 mm, p25=0.6 mm, p75=1.0 mm. The group/control difference is highly significant. Epide mio - logical model: logit (IMT)= 4.463+(2.021+value for GEN)+(0.055x AGE value)+(-3.419x RF value)+(-4.447x SM value)+(5.115x HTA value)+(3.56x DM value)+ (22.389x LIP value)+(24.206x CVD value)+(1.449x other value)+(-0.138x It score value)+(0.19xBMI value). Epidemiological-inflammatory model: logit (IMT)=5.204+ (2.545x GEN value)+(0.076x AGE value)+(-6.132x RF value)+(-7.583x SM value)+(8.744x HTA value)+(6.838x DM value)+(25.446x LIP value)+(28.825x CVD value)+ (2.487x other value)+(-0.218xIt score value)+(0.649x BMI value) +(-0.194x fibrinogen value)+(0.894x IL-6 value)+(0.659x CRP value). Values for both models Exp(B)=4.882; P of sample=0.83; logit=-0.19; OR= 23.84; model accuracy for the first model 87% and for the second 88%; Omnibus test of the first model c2=34.324; p=0.000; reliability coefficient -2LogLH=56.854; Omnibus test of the second model c2=39.774; p=0.000; and -2LogLH=51.403.
CONCLUSIONS
The ageing of blood vessels in COVID-19 can be predicted.
PubMed: 37814624
DOI: 10.5937/jomb0-39602 -
Revista Medica de Chile Dec 2018Statistical inference was introduced by Fisher and Neyman-Pearson more than 90 years ago to define the probability that the difference in results between several groups... (Review)
Review
Statistical inference was introduced by Fisher and Neyman-Pearson more than 90 years ago to define the probability that the difference in results between several groups is due to randomness or is a real, "significant" difference. The usual procedure is to test the probability (P) against the null hypothesis that there is no real difference except because of the inevitable sampling variability. If this probability is high we accept the null hypothesis and infer that there is no real difference, but if P is low (P < 0.05) we reject the null hypothesis and infer that there is, a "significant" difference. However, a large amount of discoveries using this method are not reproducible. Statisticians have defined the deficiencies of the method and warned the researchers that P is a very unreliable measure. Two uncertainties of the "significance" concept are described in this review: a) The inefficacy of a P value to discard the null hypothesis; b) The low probability to reproduce a P value after an exact replication of the experiment. Due to the discredit of "significance" the American Statistical Association recently stated that P values do not provide a good measure of evidence for a hypothesis. Statisticians recommend to never use the word "significant" because it is misleading. Instead, the exact P value should be stated along with the effect size and confidence intervals. Nothing greater than P = 0.001 should be considered as a demonstration that something was discovered. Currently, several alternatives are being studied to replace the classical concepts.
Topics: Biomedical Research; Humans; Probability; Reference Values; Sample Size; Statistics as Topic
PubMed: 30724983
DOI: 10.4067/S0034-98872018001001184 -
Proceedings of the National Academy of... Aug 2020In randomized experiments, Fisher-exact values are available and should be used to help evaluate results rather than the more commonly reported asymptotic values. One...
In randomized experiments, Fisher-exact values are available and should be used to help evaluate results rather than the more commonly reported asymptotic values. One reason is that using the latter can effectively alter the question being addressed by including irrelevant distributional assumptions. The Fisherian statistical framework, proposed in 1925, calculates a value in a randomized experiment by using the actual randomization procedure that led to the observed data. Here, we illustrate this Fisherian framework in a crossover randomized experiment. First, we consider the first period of the experiment and analyze its data as a completely randomized experiment, ignoring the second period; then, we consider both periods. For each analysis, we focus on 10 outcomes that illustrate important differences between the asymptotic and Fisher tests for the null hypothesis of no ozone effect. For some outcomes, the traditional value based on the approximating asymptotic Student's distribution substantially subceeded the minimum attainable Fisher-exact value. For the other outcomes, the Fisher-exact null randomization distribution substantially differed from the bell-shaped one assumed by the asymptotic test. Our conclusions: When researchers choose to report values in randomized experiments, 1) Fisher-exact values should be used, especially in studies with small sample sizes, and 2) the shape of the actual null randomization distribution should be examined for the recondite scientific insights it may reveal.
Topics: Cross-Over Studies; Data Interpretation, Statistical; Humans; Models, Statistical; Random Allocation; Randomized Controlled Trials as Topic; Research Personnel; Sample Size
PubMed: 32703808
DOI: 10.1073/pnas.1915454117 -
Journal of Trace Elements in Medicine... Oct 2015The German, Austrian and Swiss nutrition societies are the joint editors of the 'reference values for nutrient intake'. They have revised the reference values for the... (Review)
Review
The German, Austrian and Swiss nutrition societies are the joint editors of the 'reference values for nutrient intake'. They have revised the reference values for the intake of selenium and published them in February 2015. The saturation of selenoprotein P (SePP) in plasma is used as a criterion for the derivation of reference values for selenium intake in adults. For persons from selenium-deficient regions (China) SePP saturation was achieved with a daily intake of 49μg of selenium. When using the reference body weights the D-A-CH reference values are based upon, the resulting estimated value for selenium intake is 70μg/day for men and 60μg/day for women. The estimated value for selenium intake for children and adolescents is extrapolated using the estimated value for adults in relation to body weight. For infants aged 0 to under 4 months the estimated value of 10μg/day was derived from the basis of selenium intake via breast milk. For infants aged 4 to under 12 months this estimated value was used and taking into account the differences regarding body weight an estimated value of 15μg/day was derived. For lactating women compared to non-lactating women a higher reference value of 75μg/day is indicated due to the release of selenium with breast milk. The additional selenium requirement for pregnant women is negligible, so that no increased reference value is indicated.
Topics: Age Distribution; Feeding Behavior; Humans; Reference Values; Selenium
PubMed: 26302929
DOI: 10.1016/j.jtemb.2015.07.005 -
Problems in using p-curve analysis and text-mining to detect rate of p-hacking and evidential value.PeerJ 2016Background. The p-curve is a plot of the distribution of p-values reported in a set of scientific studies. Comparisons between ranges of p-values have been used to...
Background. The p-curve is a plot of the distribution of p-values reported in a set of scientific studies. Comparisons between ranges of p-values have been used to evaluate fields of research in terms of the extent to which studies have genuine evidential value, and the extent to which they suffer from bias in the selection of variables and analyses for publication, p-hacking. Methods. p-hacking can take various forms. Here we used R code to simulate the use of ghost variables, where an experimenter gathers data on several dependent variables but reports only those with statistically significant effects. We also examined a text-mined dataset used by Head et al. (2015) and assessed its suitability for investigating p-hacking. Results. We show that when there is ghost p-hacking, the shape of the p-curve depends on whether dependent variables are intercorrelated. For uncorrelated variables, simulated p-hacked data do not give the "p-hacking bump" just below .05 that is regarded as evidence of p-hacking, though there is a negative skew when simulated variables are inter-correlated. The way p-curves vary according to features of underlying data poses problems when automated text mining is used to detect p-values in heterogeneous sets of published papers. Conclusions. The absence of a bump in the p-curve is not indicative of lack of p-hacking. Furthermore, while studies with evidential value will usually generate a right-skewed p-curve, we cannot treat a right-skewed p-curve as an indicator of the extent of evidential value, unless we have a model specific to the type of p-values entered into the analysis. We conclude that it is not feasible to use the p-curve to estimate the extent of p-hacking and evidential value unless there is considerable control over the type of data entered into the analysis. In particular, p-hacking with ghost variables is likely to be missed.
PubMed: 26925335
DOI: 10.7717/peerj.1715 -
Zhong Nan Da Xue Xue Bao. Yi Xue Ban =... Feb 2023The number of gestational women has been increased in recent years, resulting in more adverse pregnancy outcomes. It is crucial to assess the coagulation function of...
OBJECTIVES
The number of gestational women has been increased in recent years, resulting in more adverse pregnancy outcomes. It is crucial to assess the coagulation function of pregnant women and to intervene in a timely manner. This study aims to analyze the influencing factors on thrombelastography (TEG) and explore the evaluation of TEG for gestational women.
METHODS
A retrospective study was conducted on 449 pregnant women who were hospitalized in the obstetrics department in Xiangya Hospital of Central South University from 2018 to 2020. We compared the changes on the TEG parameters among normal pregnant women between different age groups, different ingravidation groups, and different stages of pregnancy groups. The influence on TEG of hypertensive disorders in pregnancy (HDP) and gestational diabetes mellitus (GDM) as well as two diseases synchronization was explored.
RESULTS
Compared with the normal second trimester women, the R values and K values of TEG were increased, and α angle, CI values and LY30 values were decreased in third trimester women (all <0.05). Compared with normal group, the R values and CI values of TEG of the HDP group have significant difference (both <0.05). There were no significant difference of TEG between the GDM group, the HDP combined with GDM group and the normal group (all 0.05). Multiple linear regression analysis showed that the influencing factors for R value in TEG were weeks of gestation (<0.001) and mode of conception (<0.05), for α angle was weeks of gestation (<0.05), for MA value was mode of conception (<0.05), and for CI value was weeks of gestation (<0.05). The analysis of correlation between TEG with platelet (PLT) and coagulation routines represented that there was a correlation between TEG R values and activated partial thromboplastin time (APTT) (<0.01), and negative correlation between TEG CI values and APTT (<0.05). There was a negative correlation between TEG K values and FIB (<0.05). The correlation of α angle (<0.05), MA values (<0.01) and CI values (<0.05) with FIB were positive respectively.
CONCLUSIONS
The TEG parameters of 3 stages of pregnancy were different. The different ingravidation approach has effect on TEG. The TEG parameters were consistent with conventional coagulation indicators. The TEG can be used to screen the coagulation status of gestational women, recognize the abnormalities of coagulation and prevent the severe complication timely.
Topics: Female; Humans; Pregnancy; Thrombelastography; Blood Coagulation Tests; Retrospective Studies; Blood Coagulation; Blood Platelets; Diabetes, Gestational
PubMed: 36999466
DOI: 10.11817/j.issn.1672-7347.2023.210530 -
Canadian Journal of Psychiatry. Revue... Nov 2015Functional impairment continues to represent a major challenge in schizophrenia. Surprisingly, patients with schizophrenia report a level of happiness comparable with...
OBJECTIVE
Functional impairment continues to represent a major challenge in schizophrenia. Surprisingly, patients with schizophrenia report a level of happiness comparable with control subjects, even in the face of the prominent functional deficits, a finding at odds with evidence indicating a positive relation between happiness and level of functioning. In attempting to reconcile these findings, we chose to examine the issue of values, defined as affectively infused criteria or motivational goals used to select and justify actions, people, and the self, as values are related to both happiness and functioning.
METHODS
Fifty-six first-episode patients in remission and 56 healthy control subjects completed happiness and values measures. Statistical analyses included correlations, analysis of variance, structural equation modelling, and smallest space analysis.
RESULTS
Results indicated that patients with schizophrenia placed significantly greater priority on the value dimensions of Tradition (P = 0.02) and Power (P = 0.03), and significantly less priority on Self-direction (P = 0.007) and Stimulation, (P = 0.008).
CONCLUSIONS
Essentially, people with schizophrenia place more emphasis on the customs and ideas that traditional culture or religion provide in conjunction with a decreased interest in change, which is at odds with the expectations of early adulthood. This value difference could be related to functional deficits. To this point, we have assumed that people hold to the same values that guided them before the illness' onset, but this may not be the case. Our study indicates that values differ in people with schizophrenia, compared with control subjects, even early in the illness and in the face of symptomatic remission.
Topics: Adolescent; Adult; Case-Control Studies; Female; Happiness; Humans; Male; Remission Induction; Schizophrenic Psychology; Social Values; Young Adult
PubMed: 26720508
DOI: 10.1177/070674371506001106