An estimate of standard deviation of normal population based on the difference between means of two groups divided by sample mean

1954 ◽  
Vol 6 (2) ◽  
pp. 153-160
Author(s):  
Minoru Siotani
Keyword(s):  
Standard Deviation ◽  
Normal Population ◽  
Population Based ◽  
Sample Mean ◽  
The Difference

scholarly journals Prevalence of isolated gastrocnemius tightness in patients with foot and ankle pathology – a population based study

2018 ◽  
Vol 3 (3) ◽  
pp. 2473011418S0033
Author(s):  
Karan Malhotra ◽  
Oliver Chan ◽  
Nicholas Cullen ◽  
Matthew Welck ◽  
Andrew Goldberg ◽  
...  
Keyword(s):  
Normal Population ◽  
Population Based ◽  
Activity Level ◽  
Control Group ◽  
Power Calculation ◽  
Foot And Ankle ◽  
Population Based Study ◽  
The Difference ◽  
A Prospective Study ◽  
Gastrocnemius Tightness

Category: Other Introduction/Purpose: Gastrocnemius tightness (GT) is thought to predispose patients to multiple musculoskeletal pathologies including back pain, plantar fasciitis, and metatarsalgia. It is thought to be especially prevalent in patients with foot and ankle pathology (FAP) and consequently there is an emerging trend to perform lengthening / release procedures in this patient group. However, it is not clear what proportion of the normal population has GT and how this differs in patients with FAP. We set out to investigate what the incidence and degree of GT in the foot and ankle population is compared to the normal population. Methods: This was a prospective study comparing GT in a cohort of patients with FAP with GT in controls matched for age, gender, and ethnicity. The control group consisted of healthy adult volunteers and the FAP group consisted of patients presenting to our Foot & Ankle unit. Patients with previous surgery, tendoachilles tightness, or ankle arthritis were excluded. GT was measured using a digital inclinometer and the lunge test. It was calculated as the difference between maximal ankle dorsiflexion with the knee extended and with the knee flexed. Data on the control group was collected first and a power calculation suggested a FAP cohort size of 91 feet was required to detect a 2° difference in GT (a= 0.05, ß = 0.05, Ratio 3:1). Results: After case-matching 97 FAP cases were paired with 291 controls for analysis. Mean GT was 8.0° ±5.7° (range: 0-21°) in FAP patients versus 6.0° ±3.5° (range: 0-16°) in controls (p<0.001). Regression analysis demonstrated demographics including BMI and activity level were not significant determinants of GT in the FAP group (r=0.141, p=0.599). Subgroup analysis of the FAP group revealed a mean GT of 10.3° ±6.0° in patients with forefoot pathology (FoP) versus 6.9° ±5.3° in the other FAP patients (NFoP) (p=0.008). When comparing the NFoP group to the controls, there was no difference in GT (p=0.188). In total 21 FAP patients (21.6%) and 12 FoP patients (37.5%) had GT greater than 2 standard deviations of the control group (Figure 1). Conclusion: This population based study demonstrates increased GT in the FAP population versus the normal population; however, in patients without forefoot pathology, this difference may not be clinically relevant. Over a third of patients with forefoot pathology have GT which is greater than the normal population range. We conclude that not all patients with foot and ankle pathology have inherently increased GT, compared with the normal population, but it is reasonably common in patients with forefoot pathology. Further work is required to define what degree of GT may be considered significant, to determine which patients will benefit from surgical treatment.

scholarly journals Admissible and minimax estimation of the parameters of the selected normal population in two-stage adaptive designs under reflected normal loss function

2019 ◽  
Vol 39 (2) ◽  
pp. 361-383
Author(s):  
Hasan Mazarei ◽  
Nader Nematollahi
Keyword(s):  
Loss Function ◽  
Adaptive Design ◽  
Normal Population ◽  
Sufficient Conditions ◽  
Real Data ◽  
Population Based ◽  
Two Stage ◽  
Sample Mean ◽  
Data Application ◽  
Minimax Estimators

In clinical research, one of the key problems is to estimate the effect of the best treatment among the given k treatments in two-stage adaptive design. Suppose the effects of two treatments have normal distributions with means θ1 and θ2, respectively, and common known variance σ2. In the first stage, random samples of size n1 with means X1 and X2 are chosen from the two populations. Then the population with the larger or smaller sample mean XM is selected, and a random sample of size n2 with mean YM is chosen from this population in the second stage of design. Our aim is to estimate the mean θM or θJ of the selected population based on XM and YM in two-stage adaptive design under the reflected normal loss function. We obtain minimax estimators of θM and θJ, and then provide some sufficient conditions for the inadmissibility of estimators of θM and θJ. Theoretical results are augmented with a simulation study as well as a real data application.

SOCIOECONOMIC STATUS AND BLACK AND WHITE INTELLIGENCE REVISITED

1980 ◽  
Vol 8 (2) ◽  
pp. 233-237 ◽  
Author(s):  
Douglas Tate ◽  
Gail Gibson
Keyword(s):  
Standard Deviation ◽  
Middle Class ◽  
Youth Development ◽  
Black Youth ◽  
Lower Class ◽  
Black Middle Class ◽  
Sample Mean ◽  
Black And White ◽  
Blacks And Whites ◽  
The Difference

The mean average difference previously recorded between blacks and whites on intelligence may be an artifact based upon the differences in education and socioeconomic position of blacks and whites in this country. Previous studies in this area, with a few exceptions, have been comparing lower class blacks with second-third through tenth generation middle class whites. Only recently in this country has a true black middle class emerged that has had access to both education and income. Even though black income nationally is still only 61% of white income, the black middle class income has approached 75% of white income. This increase in disposable income is being invested in youth development. Second generation black youth of middle class status will show many attributes of the American achievement syndrome. The black youth in this study exceeded the white sample mean on the Stanford-Binet and the WISCR. The black mean was 128.63 with a standard deviation of 14.44, while the white mean was 115.75 with a standard deviation of 13.37. The difference was significant at the 0.001 level.

scholarly journals Understanding the Difference Between Standard Deviation and Standard Error of the Mean, and Knowing When to Use Which

2020 ◽  
Vol 42 (4) ◽  
pp. 409-410
Author(s):  
Chittaranjan Andrade
Keyword(s):  
Standard Deviation ◽  
Confidence Interval ◽  
Standard Error ◽  
Statistical Significance ◽  
Sample Mean ◽  
Population Mean ◽  
Sample Data ◽  
The Mean ◽  
The Difference

Many authors are unsure of whether to present the mean along with the standard deviation (SD) or along with the standard error of the mean (SEM). The SD is a descriptive statistic that estimates the scatter of values around the sample mean; hence, the SD describes the sample. In contrast, the SEM is an estimate of how close the sample mean is to the population mean; it is an intermediate term in the calculation of the 95% confidence interval around the mean, and (where applicable) statistical significance; the SEM does not describe the sample. Therefore, the mean should always be accompanied by the SD when describing the sample. There are many reasons why the SEM continues to be reported, and it is argued that none of these is justifiable. In fact, presentation of SEMs may mislead readers into believing that the sample data are more precise than they actually are. Given that the standard error is not presented for other parameters, such as difference between means or proportions, and difference between proportions, it is suggested that presentation of SEM values can be done away with, altogether.

scholarly journals Arithmetic hip-knee-ankle angle (aHKA): An algorithm for estimating constitutional lower limb alignment in the arthritic patient population

2021 ◽  
Vol 2 (5) ◽  
pp. 351-358
Author(s):  
William Griffiths-Jones ◽  
Darren B. Chen ◽  
Ian A. Harris ◽  
Johan Bellemans ◽  
Samuel J. MacDessi
Keyword(s):  
Lower Limb ◽  
Normal Population ◽  
Population Based ◽  
Normal Group ◽  
Limb Alignment ◽  
Cross Sectional ◽  
Straightforward Method ◽  
Significant Difference ◽  
Total Knee ◽  
The Difference

Aims Once knee arthritis and deformity have occurred, it is currently not known how to determine a patient’s constitutional (pre-arthritic) limb alignment. The purpose of this study was to describe and validate the arithmetic hip-knee-ankle (aHKA) algorithm as a straightforward method for preoperative planning and intraoperative restoration of the constitutional limb alignment in total knee arthroplasty (TKA). Methods A comparative cross-sectional, radiological study was undertaken of 500 normal knees and 500 arthritic knees undergoing TKA. By definition, the aHKA algorithm subtracts the lateral distal femoral angle (LDFA) from the medial proximal tibial angle (MPTA). The mechanical HKA (mHKA) of the normal group was compared to the mHKA of the arthritic group to examine the difference, specifically related to deformity in the latter. The mHKA and aHKA were then compared in the normal group to assess for differences related to joint line convergence. Lastly, the aHKA of both the normal and arthritic groups were compared to test the hypothesis that the aHKA can estimate the constitutional alignment of the limb by sharing a similar centrality and distribution with the normal population. Results There was a significant difference in means and distributions of the mHKA of the normal group compared to the arthritic group (mean -1.33° (SD 2.34°) vs mean -2.88° (SD 7.39°) respectively; p < 0.001). However, there was no significant difference between normal and arthritic groups using the aHKA (mean -0.87° (SD 2.54°) vs mean -0.77° (SD 2.84°) respectively; p = 0.550). There was no significant difference in the MPTA and LDFA between the normal and arthritic groups. Conclusion The arithmetic HKA effectively estimated the constitutional alignment of the lower limb after the onset of arthritis in this cross-sectional population-based analysis. This finding is of significant importance to surgeons aiming to restore the constitutional alignment of the lower limb during TKA. Cite this article: Bone Jt Open 2021;2(5):351–358.

scholarly journals A new customised placental weight standard redefines the relationship between maternal obesity and extremes of placental size and is more closely associated with pregnancy complications than an existing population standard

2019 ◽  
Vol 11 (4) ◽  
pp. 350-359
Author(s):  
Jacqueline M. Wallace ◽  
Joeleita P. Agard ◽  
Graham W. Horgan
Keyword(s):  
Pregnancy Complications ◽  
Maternal Obesity ◽  
Population Based ◽  
Multiple Regression Model ◽  
Placental Weight ◽  
Morbidly Obese ◽  
Obese Women ◽  
Entire Cohort ◽  
Multiparous Women ◽  
The Difference

AbstractPlacental weight is a valuable indicator of its function, predicting both pregnancy outcome and lifelong health. Population-based centile charts of weight-for-gestational-age and parity are useful for identifying extremes of placental weight but fail to consider maternal size. To address this deficit, a multiple regression model was fitted to derive coefficients for predicting normal placental weight using records from healthy pregnancies of nulliparous/multiparous women of differing height and weight (n = 107,170 deliveries, 37–43 weeks gestation). The difference between actual and predicted placental weight generated a z-score/individual centile for the entire cohort including women with pregnancy complications (n = 121,591). The association between maternal BMI and placental weight extremes defined by the new customised versus population-based standard was investigated by logistic regression, as was the association between low placental weight and pregnancy complications. Underweight women had a greater risk of low placental weight [<10thcentile, OR 1.84 (95% CI 1.66, 2.05)] and obese women had a greater risk of high placental weight [>90th centile, OR 1.98 (95% CI 1.88, 2.10)] using a population standard. After customisation, the risk of high placental weight in obese/morbidly obese women was attenuated [OR 1.17 (95% CI 1.09, 1.25)]/no longer significant, while their risk of low placental weight was 59%–129% higher (P < 0.001). The customised placental weight standard was more closely associated with stillbirth, hypertensive disease, placental abruption and neonatal death than the population standard. Our customised placental weight standard reveals higher risk of relative placental growth restriction leading to lower than expected birthweights in obese women, and a stronger association between low placental weight and pregnancy complications generally. Further, it provides an alternative tool for defining placental weight extremes with implications for the placental programming of chronic disease.

scholarly journals Effects of marital status on overall and cancer-specific survival in laryngeal cancer patients: a population-based study

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Zhao Ding ◽  
Deshun Yu ◽  
Hefeng Li ◽  
Yueming Ding
Keyword(s):  
Marital Status ◽  
Cancer Patients ◽  
Laryngeal Cancer ◽  
Cox Regression ◽  
Group Analysis ◽  
Population Based ◽  
Cancer Specific Survival ◽  
Cox Regression Analysis ◽  
Prognostic Effect ◽  
The Difference

AbstractMarital status has long been recognized as an important prognostic factor for many cancers, however its’ prognostic effect for patients with laryngeal cancer has not been fully examined. We retrospectively analyzed 8834 laryngeal cancer patients in the Surveillance Epidemiology and End Results database from 2004 to 2010. Patients were divided into four groups: married, widowed, single, and divorced/separated. The difference in overall survival (OS) and cancer-specific survival (CSS) of the various marital subgroups were calculated using the Kaplan–Meier curve. Multivariate Cox regression analysis screened for independent prognostic factors. Propensity score matching (PSM) was also conducted to minimize selection bias. We included 8834 eligible patients (4817 married, 894 widowed, 1732 single and 1391 divorced/separated) with laryngeal cancer. The 5-year OS and CSS of married, widowed, single, and separated/divorced patients were examined. Univariate and multivariate analyses found marital status to be an independent predictor of survival. Subgroup survival analysis showed that the OS and CSS rates in widowed patients were always the lowest in the various American Joint Committee on Cancer stages, irrespective of sex. Widowed patients demonstrated worse OS and CSS in the 1:1 matched group analysis. Among patients with laryngeal cancer, widowed patients represented the highest-risk group, with the lowest OS and CSS.

scholarly journals Intravenous Immunoglobulin Treatment in Kawasaki Disease Decreases the Incidence of Myopia

2021 ◽  
Vol 10 (7) ◽  
pp. 1381
Author(s):  
Hun-Ju Yu ◽  
Meng-Ni Chuang ◽  
Chiao-Lun Chu ◽  
Pei-Lin Wu ◽  
Shu-Chen Ho ◽  
...  
Keyword(s):  
Kawasaki Disease ◽  
Intravenous Immunoglobulin ◽  
Systemic Vasculitis ◽  
Age Distribution ◽  
Population Based ◽  
Research Database ◽  
Ocular Manifestations ◽  
Missing Data Treatment ◽  
The Difference ◽  
Age Range

Kawasaki disease (KD) is a systemic vasculitis that primarily affects children under the age of 5 years old. The most significant complication is coronary artery lesions, but several ocular manifestations have also been reported. Recently, one study revealed an increasing incidence of myopia among KD patients. Therefore, the aim of this study was to assess the difference in myopic incidence between Kawasaki disease (KD) patients treated with aspirin and intravenous immunoglobulin (IVIG). Materials and methods: We carried out a nationwide retrospective cohort study by analyzing the data of KD patients (ICD-9-CM code 4461) from Taiwan’s National Health Insurance Research Database (NHIRD) during the period of 1996–2013. Results: A total of 14,102 diagnosed KD were found in Taiwan during the study period. After excluded missing data, treatment strategy and age distribution, a total of 1446 KD patients were enrolled for analysis including 53 of which received aspirin (without IVIG) and 1393 of which were treated with IVIG. Patients who had myopia, astigmatism, glaucoma, cataract, etc. prior to their KD diagnosis were excluded. The age range was 0 to 6 years old. According to the cumulative curves, our results demonstrated that the myopic incidence in the IVIG group was significantly lower than the aspirin group (hazard ratio: 0.59, 95% confidence intervals: 0.36~0.96, p = 0.02). Treatment with IVIG for KD patients may have benefit for myopia control. Conclusion: Compared to aspirin, IVIG may decrease the myopic risk in KD patients. However, it needs further investigation including clinical vision survey of myopia due to the limitations of this population-based study.

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