According to the central limit theorem, the means of a random sample of size, n, from a population with mean, µ, and variance, σ2, distribute normally with mean, µ, and variance, . Using the central limit theorem, a variety of parametric tests have been developed under assumptions about the parameters that determine the population probability distribution. Compared to non-parametric tests, which do not require any assumptions about the population probability distribution, parametric tests produce more accurate and precise estimates with higher statistical powers. However, many medical researchers use parametric tests to present their data without knowledge of the contribution of the central limit theorem to the development of such tests. Thus, this review presents the basic concepts of the central limit theorem and its role in binomial distributions and the Student's t-test, and provides an example of the sampling distributions of small populations. A proof of the central limit theorem is also described with the mathematical concepts required for its near-complete understanding.

Missing values and outliers are frequently encountered while collecting data. The presence of missing values reduces the data available to be analyzed, compromising the statistical power of the study, and eventually the reliability of its results. In addition, it causes a significant bias in the results and degrades the efficiency of the data. Outliers significantly affect the process of estimating statistics (e.g., the average and standard deviation of a sample), resulting in overestimated or underestimated values. Therefore, the results of data analysis are considerably dependent on the ways in which the missing values and outliers are processed. In this regard, this review discusses the types of missing values, ways of identifying outliers, and dealing with the two.

We evaluated the mental health burden of coronavirus disease (COVID-19) on physical therapists, including their stress and anxiety levels, who were at risk of developing psychological distress and other mental health symptoms. A questionnaire survey was conducted with physical therapists of three university hospitals in South Korea on 10 April 2020. The questionnaires evaluated the presence of anxiety and depression in the respondents. Among the 65 physical therapists who completed our survey, 21 (32.3%) and 12 (18.5%) physical therapists reported having symptoms of anxiety and depression, respectively. If a physical therapist was living with a ≤6-year-old infant or child, the possibility of the presence of anxiety was significantly higher. The risk of depression among those who were in their 30 s and 50 s was significantly higher than among those in their 20 s. Thus, physical therapists living with a ≤6-year-old infant or child and those in their 30 s and 50 s need special attention.

The purpose of the present study was to investigate the prevalence and incidence of gout in Korea and predict the future prevalence and incidence of gout. Data were collected from the national health claims database. Patients who had at least one claim for gout between 2007 and 2015 were included in the study. The prevalence of gout from 2007 to 2015 and the incidence of gout from 2009 to 2015 were determined. We estimated sex- and age-specific prevalence and incidence of gout during the period. The prevalence and incidence of gout were predicted using time series analysis. The prevalence of gout (95% CI) increased from 3.49 (3.48-3.51) per 1000 persons in 2007 to 7.58 (7.55-7.60) per 1000 persons in 2015. The incidence of gout (95% CI) was 1.52 (1.51-1.53) in 2009 and rose to 1.94 (1.93-1.95) per 1000 persons in 2015. The prevalence and incidence of gout were higher in men than in women. The older population had a higher prevalence and incidence than the younger population. The increase in prevalence was higher in the older population than the younger population, whereas the increase in incidence was higher in the younger population than the older population. The predicted prevalence and incidence of gout (95% CI) in 2025 were 16.59 (15.85-17.34) per 1000 persons and 3.81 (3.14-4.47) per 1000 persons. The prevalence and incidence of gout increased in Korea between 2007 and 2015. Men and the older population had a higher prevalence and incidence of gout compared to women and the younger population. However, the incidence of gout in the younger population has increased rapidly in recent years.

BACKGROUND: To date only few data have been available relating to the oncologic safety of intersphincteric resection in such advanced tumors. OBJECTIVE: This study aimed to elucidate the oncologic outcomes and clinical factors affecting the long-term survival of patients who underwent preoperative chemoradiotherapy followed by intersphincteric resection for locally advanced rectal cancers. DESIGN: This was a retrospective analysis of prospectively collected departmental data. SETTINGS: The study was conducted at a department of colorectal surgery in a tertiary care teaching hospital between January 2009 and September 2015. PATIENTS: A cohort of 147 consecutive patients with low rectal cancer undergoing intersphincteric resection after preoperative chemoradiotherapy was included. MAIN OUTCOME MEASURES: Kaplan–Meier analyses were used to evaluate the 3-year disease-free survival and local recurrence rates. Logistic regression analyses were used to analyze the influence of tumor response and other prognostic factors on survival outcomes. RESULTS: Median follow-up was 34 months (range, 8–94 mo). The estimated overall 3-year disease-free survival and local recurrence rates were 64.9% and 11.7%. Circumferential resection margin involvement and pathologic T stage (ypT stage) were significant predictors of cancer relapse. The 3-year disease-free survival was 47.4% for patients with ypT3 tumors compared with 82.0% for those with ypT0–2 tumors (p = 0.001). The 3-year disease-free survival was 36.5% for patients with involved circumferential resection margins compared with 69.7% for those with a noninvolved circumferential resection margin (p = 0.003). On multivariate analysis, ypT stage, ymrT stage, and circumferential resection margin status were associated with worse disease-free survival. Clinical T-stage and pathologic distal margin status were not independent factors affecting oncologic outcomes. LIMITATIONS: This study is limited with respect to its retrospective design. CONCLUSIONS: In these patients with locally advanced low rectal cancers, intersphincteric resection after preoperative chemoradiotherapy was associated with acceptable oncologic outcomes. See Video Abstract at http://links.lww.com/DCR/A941.