In statistic tests, the probability distribution of the statistics is important. When samples are drawn from population N (micro, sigma2) with a sample size of n, the distribution of the sample mean X should be a normal distribution N (micro, sigma2/n). Under the null hypothesis micro = micro0, the distribution of statistics z=X-micro0/sigma/radical(n) should be standardized as a normal distribution. When the variance of the population is not known, replacement with the sample variance s2 is possible. In this case, the statistics X-micro0/s/radical(n) follows a t distribution (n-1 degrees of freedom). An independent-group t test can be carried out for a comparison of means between two independent groups, with a paired t test for paired data. As the t test is a parametric test, samples should meet certain preconditions, such as normality, equal variances and independence.
Biostatistics ; Matched-Pair Analysis ; Normal Distribution ; Sample Size

Disability weight for each disease plays a key role in combining years lived with disability and years of life lost in disability adjusted life year. For the Korean Burden of Disease 2012 study, we have conducted a re-estimation of disability weights for causes of disease by adapting the methodology of a recent Global Burden of Disease study. Our study was conducted through a self-administered web-based survey using a paired comparison (PC) as the main valuation method. A total of 496 physicians and medical college students who were attending in third or fourth grade of a regular course conducted the survey. We applied a probit regression on the PC data and computed the predicted probabilities of each cause of disease from the coefficient estimates of the probit regression. We used 'being dead (1)' and 'full health (0)' as anchor points to rescale the predicted probability of each cause of disease on a scale of 0 to 1. By this method, disability weights for a total of 228 causes of disease were estimated. There was a fairly high correlation between the disability weights of overlapping causes of disease from this study and a previous South Korean study despite the differences in valuation methods and time periods. In conclusion, we have shown that disability weights can be estimated based on a PC by including 'full health' and 'being dead' as anchor points without resorting to a person trade-off. Through developments in the methodology of disability weights estimation from this study, disability weights can be easily estimated and continuously revised.
Health Resorts ; Humans ; Matched-Pair Analysis ; Methods ; Quality-Adjusted Life Years ; Republic of Korea ; Weights and Measures*

OBJECTIVES: This double-blind randomized placebo-controlled clinical trial evaluated the ability of a desensitizing agent and a self-etch adhesive on cervical dentin sensitivity (CDS) after periodontal surgery. MATERIALS AND METHODS: Ninety hypersensitive teeth of 13 subjects were included in the study. After periodontal surgery, the teeth of each posterior sextant treated with one of the following materials: G1: Clearfil S³ Bond (Kuraray Dental), G2: Gluma Desensitizer (Heraeus Kulzer), and G3: placebo (water). The sensitivity was assessed using evaporative stimuli before treatment (baseline, T0), 1 day after treatment (T1), after 1 week (T2), and after 1 month (T3) according to visual analog scale (VAS). RESULTS: Following the treatment, all the 3 groups showed significant reduction of CDS in T1 compared to T0. Reduction of CDS between T1 and T2 was observed only in G1 but there was no significant difference between T2 and T3 in this group. Although we observed a significant difference in T3 compared to T1 and T2 in G2 and G3, comparison of treatment groups in each assessment time showed a significant difference only in T3. According to paired comparison, this was due to the difference between G2 and G3. CONCLUSIONS: Dentin sensitivity following periodontal surgery will decrease spontaneously over time, but treating the sensitive teeth with Gluma Desensitizer and Clearfil S³ Bond can have some benefits.
Adhesives* ; Dentin Sensitivity* ; Dentin* ; Matched-Pair Analysis ; Tooth ; Visual Analog Scale

BACKGROUND: The objective of this study was to evaluate the diagnostic efficiency of the Comprehensive Attention Test (CAT) by comparing the results of the continuous performance test (CPT) and the CAT in children and adolescents with attention-deficit hyperactivity disorder (ADHD). METHOD: A total of 110 children and adolescents with ADHD (mean age : 11.2+/-2.9 years, 76 boys) and 36 children and adolescents without ADHD (mean age : 12.0+/-2.7 years, 25 boys) completed the CAT. We compared the specificity and sensitivity of the CPT and CAT at two different cut-off points via the McNemar test. The areas under the receiver operating characteristic curves (AUC) between the two groups were compared using Medcalc software. RESULTS: The sensitivity and specificity of the CPT were .419 and .806, respectively. The sensitivity of the CAT was .827, which was significantly higher than that of the CPT (p<.001), and the specificity of CAT is .444, which was significantly lower than that of CPT (p<.001). The AUC of the CPT and CAT was .664 and .692, respectively, and there were no significant difference between the two groups on the paired comparison (p=.513). CONCLUSIONS: The results of this study suggest that the CAT has moderate specificity and high sensitivity. The CAT can be used as a useful tool to evaluate the neuropsychological function of children and adolescents with ADHD.
Adolescent ; Animals ; Area Under Curve ; Cats ; Child ; Humans ; Matched-Pair Analysis ; ROC Curve ; Sensitivity and Specificity

BACKGROUND: The objective of this study was to evaluate the diagnostic efficiency of the Comprehensive Attention Test (CAT) by comparing the results of the continuous performance test (CPT) and the CAT in children and adolescents with attention-deficit hyperactivity disorder (ADHD). METHOD: A total of 110 children and adolescents with ADHD (mean age : 11.2+/-2.9 years, 76 boys) and 36 children and adolescents without ADHD (mean age : 12.0+/-2.7 years, 25 boys) completed the CAT. We compared the specificity and sensitivity of the CPT and CAT at two different cut-off points via the McNemar test. The areas under the receiver operating characteristic curves (AUC) between the two groups were compared using Medcalc software. RESULTS: The sensitivity and specificity of the CPT were .419 and .806, respectively. The sensitivity of the CAT was .827, which was significantly higher than that of the CPT (p<.001), and the specificity of CAT is .444, which was significantly lower than that of CPT (p<.001). The AUC of the CPT and CAT was .664 and .692, respectively, and there were no significant difference between the two groups on the paired comparison (p=.513). CONCLUSIONS: The results of this study suggest that the CAT has moderate specificity and high sensitivity. The CAT can be used as a useful tool to evaluate the neuropsychological function of children and adolescents with ADHD.
Adolescent ; Animals ; Area Under Curve ; Cats ; Child ; Humans ; Matched-Pair Analysis ; ROC Curve ; Sensitivity and Specificity

BACKGROUND: The Korean Medical Association intends to determine the relative value of physician's work separately from the total relative value scale for each medical or surgical procedure. This study was designed by the Korean Society for Laboratory Medicine to determine the relative value of laboratory physician's work (LPW) in each diagnostic test. The LPW was clearly defined first and then its relative value was measured quantitatively on the basis of time and intensity of work. METHODS: LPW in the laboratory test was categorized into three parts, pre-service, intra-service, and post-service. The relative value of physician's work was measured using Rasch paired comparisons. RESULTS: Practice characteristics of LPW were clearly defined according to the pre-service, intraservice, and post-service. However, any laboratory physician's effort to improve the quality of laboratory work, which could not be measured in each test, had to be comprised in a pre-service designated separately as `comprehensive pre-service'. Rasch analysis based on the rating survey for LPW taken by a diverse group of laboratory medicine and other medical specialists revealed higher values than those assigned previously in many routine diagnostic tests (e.g., Gram stain, hemoglobin, anti-HBs, ABO cell type). The results obtained by applying Rasch regression analysis showed that the diagnostic tests that had been given a low relative value of LPW tended to be measured with more improved relative valuation. CONCLUSIONS: LPW for quality control and quality improvement was acknowledged with an improved relative valuation, even in the routine diagnostic test, as the results of Rasch analysis based on the rating survey. LPW might be further equated across the specialties, considering the practice characteristics of LPW.
Diagnostic Tests, Routine ; Matched-Pair Analysis ; Quality Control ; Quality Improvement ; Relative Value Scales ; Specialization

OBJECTIVES: To investigate the effect of electrical automatic massage (EAM) at bedtime on sleep quality and fatigue. METHODS: We recruited consecutively 35 adults (23 male, 48.7±8.07 y) who complained of poor sleep (Pittsburgh Sleep Quality Index≥5) and fatigue (Chalder Fatigue Scale≥4). This is a cross over study including two consecutive sleep studies with or without EAM. The EAM session includes preset ‘sleep mode’, which last 30 minutes covering whole body. Participants were seated in the commercially available massage chair (REX-L®) under the calm and dim light condition immediately before polysomnography. Participants reported perceived sleep latency, sleep duration, and fatigue using visual analogue scale following morning. RESULTS: Polysomnography parameters and subjective reports were compared between sleep with EAM and sleep without EAM. Paired comparison on average revealed sleep structure improvement N1 (13.6→10.9%) and N2 sleep (59.3→57.2%) decreased, and N3 sleep increased (3.0→6.4%), as well as sleep latency (10.3→5.6 min). Improvement in arousal index (17.1→13.0/h) and apnea-hypopnea index (9.1→7.0/h) were also seen following sleep after EAM. Sleep efficiency and total sleep time were not changed by EAM. Participants subjective reports also indicated better sleep on EAM; more lengthened sleep (306→330 minutes) and more relieved fatigue significantly after EAM. CONCLUSIONS: This study demonstrated that muscle relaxation through EAM at bedtime may improve the sleep and alleviate fatigue. It suggests that EAM may be one of alternatives to promote sleep quality. Further studies in a clinical setting are warranted to support this finding.
Adult ; Arousal ; Fatigue* ; Humans ; Male ; Massage* ; Matched-Pair Analysis ; Muscle Relaxation ; Polysomnography ; Relaxation

PURPOSE: To compare the clinical efficacy of iopamidol 370 and iopromide 370, as used in hepatic arteriography, in terms of their safety, patient tolerance, and image quality. MATERIALS AND METHODS: Between February and April 2001, 30 patients (M:F=27:3; mean age, 57 years) with hepatocellular carcinoma underwent hepatic angiography in which iopamidol 370 was used for transcatheter arterial chemoembolization (TAE). Sensations of heat or pain following contrast injection, a patient's distress or discomfort levels, and any side effects of the contrast media were monitored, and afterwards patients were asked whether they were aware of any differences between iopamidol 370 and iopromide 370, which had been used in hepatic angiography for previous TAE prior to February 2001. Three experienced independent radiologists assessed the diagnostic efficacy of the contrast media in terms of overall image quality, which was statistically analysed using Wilcoxon's signed ranks test. RESULTS: No patient experienced sensations of heat or pain during angiography, or showed any objective distress or discomfort, though two suffered mild nausea during angiography with iopamidol 370. None was aware of any difference between iopromide 370 and iopamidol 370. In terms of overall image quality, the diagnostic efficacy of contrast media in all patients was 'good'to 'excellent', with no significant difference between iopromide 370 and iopamidol 370 (p>0.05). CONCLUSION: In hepatic arteriography, the clinical efficacy of iopamidol 370 is comparable with that of another nonionic contrast medium, iopromide 370, in terms of safety, tolerance, and image quality. Iopamidol 370 is thus a useful alternative medium.
Angiography* ; Carcinoma, Hepatocellular ; Contrast Media ; Hot Temperature ; Humans ; Iopamidol* ; Matched-Pair Analysis* ; Nausea ; Patient Safety ; Sensation

OBJECTIVETo indicate the deficiency of the classical method for analyzing data on individual matching case-control study in consideration of the interaction between the study factor (exposure) and the matching factor, and to find out a proper method for handling this deficiency.

METHODFirst, experimental data with 50 pairs of cases and controls were used for strata analysis according to the values of a matching factor to illustrate the possible interaction between a risk factor (exposure) and the matching factor. Second, a detailed procedure was proposed for analyzing such data.

RESULTSInteraction between the study factor and matching factor was demonstrated by using strata analysis and unconditional logistic regression analysis. Therefore the results from the classical analysis for such data might be incorrect.

CONCLUSIONData from individual matching case-control study design should be dealt with strata analysis or multivariate analysis to explore and evaluate the possible interaction between the study factor and matching factor. The conclusion would be valid only after such analysis is conducted.

The safety and efficacy of the CO2laser as a replacement for the steel scalpel is well documented in plastic surgery, but the use of the laser blepharoplasty has been controversy. This study compares and contrasts the use of the CO2 laser with conventional method in cosmetic upper eyelid blepharoplasty. Thirteen Patients underwent blepharoplasty in a paired comparison study. Four patients(Group A) underwent blepharoplasty by laser, another four patients (Group B) underwent blepharoplasty by conventional method, and the other five patients(Group C) underwent upper eyelid blepharoplasty using the laser on one eye and a conventional method on the other side. Preoperative factor(set up time, equipment), intraoperative factor(actual operation time, bleeding, visibility), postoperative factor(swelling, ecchymosis, immediate & short term result) were evaluated. The advantage of using the CO2 laser rather than the steel scalpel in blepharoplasty are less bleeding and superior intraoperative visibility. The disadvantage of using the laser compared with steel scalpel include the cost of purchasing and maintaining the laser equipment, the need for additional and extensive laser training for surgeons and assistants, and the need for two assistants rather than the one needed for scalpel surgery There were no complications with either the scalpel or the laser.
Bleeding Time ; Blepharoplasty* ; Carbon Dioxide* ; Carbon* ; Ecchymosis ; Eyelids* ; Hemorrhage ; Humans ; Lasers, Gas* ; Matched-Pair Analysis ; Steel ; Surgery, Plastic