No abstract available.
Sample Size*

No abstract available.
Sample Size*

No abstract available
Sample Size*

At first, we review a sample size estimation method for log-rank test in survival analysis. Although it is widely used these days, it has a weakness for practical use. We propose a modification method to avoid the weakness.
Sample Size*

Repeated measures designs are widely used in the field of anesthesiology because they allow the detection of within-person change over time and provide a higher statistical power for detecting differences than a single measure design while reducing the costs and efforts to conduct a study. However, the complex process of calculating the sample size for repeated measures design requires profound statistical knowledge and also programming skills in some instances. In the present article, the author describes 1) the basic statistics for repeated measures design, 2) the explanation for G Power software, and 3) how to calculate the sample size using an example.
Anesthesiology ; Sample Size*

No abstract available.
Analysis of Variance* ; Sample Size*

The purpose of clinical trials is to find evidences for the effects of experimental new drugs or treatments on human. For the successful clinical trials, it is not sufficient to use statistics only for the analyses of collected data, but it is necessary to extend the usage of statistics in various ways. At the beginning of the study, one needs to use statistics for systematically and concretly planning the study. For this, we discussed the usage of statistics in defining the effect, determining the sample size, statistical analyses, and so on.
Humans ; Sample Size

The proper use of statistics in medical studies is very important to draw an objective conclusion. The misuse and misunderstanding of statistics degrade the quality of scientific results. Authors should make an effort to choose proper statistical procedures and report the results appropriately. In this article, we review and summarize aspects of statistical consideration in preparing for publication in medical journals.
Publications ; Sample Size

Sample size computations, which should be done at the planning stage of the study, are necessary for research to estimate a population parameter or test a hypothesis. For causal analysis of observational databases, sample size computations are generally not needed. Post-hoc power analyses, which are typically done with non-significant findings, should not be performed since reporting post-hoc power is nothing more than reporting p values differently. While sample size calculations are typically based on the tradition of significance testing, sample size calculations based on precision are feasible – if not preferred – alternatives. Sample size calculations depend on several factors such as the study objective, scale of measurement of the outcome variable, study design, and sampling design. Computing for sample size is not as straightforward as presented in textbooks but specific strategies may be resorted to in the face of challenges and constraints.
Sample Size ; Power, Psychological

There have been many studies about marginal discrepancy of single restorations made by various systems and materials.But many of statistical inferences are not definite because of sample size,measurement number,measuring instruments,etc. The purpose of this study was to compare the marginal adaptations of the anterior single restorations made by different systems and to consider more desirable statistical methods in analysing the marginal fit.The in vitro marginal discrepancies of three different all-ceramic crown systems(Celay In-Ceram,Conventional In-Ceram,IPS Empress 2 layering technique)and one control group (PFM)were evaluated and compared.The crowns were made from one extracted maxillary central incisor prepared with a 1mm shoulder margin and 6 taper walls by milling machine.10 crowns per each system were fabricated.Measurements of a crown were recorded at 50 points that were randomly selected for marginal gap evaluation.Non-parametric statistical analysis was performed for the results. Within the limits of this study,the following conclusions were drawn: 1.Mean gap dimensions and standard deviations at the marginal opening for the maxillary incisor crowns were 98.2+/-40.6 mu m for PFM,83.5+/-18.7 mu m for Celay In-Ceram,104.9+/-44.1 mu m for conventional In-Ceram,and 45.5+/-11.5 mu m for IPS Empress 2 layering technique.The IPS Empress 2 system showed the smallest marginal gap (P<0.05).The marginal openings of the other three groups were not significantly different (P<0.05). 2.The marginal discrepancies found in this study were all within clinically acceptable standards(100 150 mu m). 3.When the variable is so controlled that the system may be the only one,mean value is interpreted to be the marginal discrepancy of a restoration which is made by each system and standard deviation is to be technique-sensitivity of each one. 4.From the standard deviations,the copy-milling technique (Celay/In-Ceram)was not considered to be technique-sensitive in comparison with other methods. 5.Parametric analysis is more reliable than non-parametric one in interpretation of the mean and standard deviation.The sample size of each group has to be more than 30 to use parametric statistics. The level of clinically acceptable marginal fit has not been established.Further studies are needed.
Crowns* ; Incisor ; Sample Size ; Shoulder