Target and actual sample sizes for studies from two trial registries from 1999 to 2020: an observational study

ObjectivesTo investigate differences between target and actual sample sizes, and what study characteristics were associated with sample sizes.DesignObservational study.SettingThe large trial registries of clinicaltrials.gov (starting in 1999) and ANZCTR (starting in 2005) through to 2021.ParticipantsOver 280 000 interventional studies excluding studies that were withheld, terminated for safety reasons or were expanded access.Main outcome measuresThe actual and target sample sizes, and the within-study ratio of the actual to target sample size.ResultsMost studies were small: the median actual sample sizes in the two databases were 60 and 52. There was a decrease over time in the target sample size of 9%–10% per 5 years, and a larger decrease of 18%–21% per 5 years for the actual sample size. The actual-to-target sample size ratio was 4.1% lower per 5 years, meaning more studies (on average) failed to hit their target sample size.ConclusionRegistered studies are more often under-recruited than over-recruited and worryingly both target and actual sample sizes appear to have decreased over time, as has the within-study gap between the target and actual sample size. Declining sample sizes and ongoing concerns about underpowered studies mean more research is needed into barriers and facilitators for improving recruitment and accessing data.

Study on the determination of felodipine sample content by fluorescence method and its application

This experiment researched and constructed a complex with good fluorescence properties, which can be used to detect the content of felodipine. It provides a new and reliable method for the determination of felodipine. The actual sample of felodipine was successfully tested, and the test result was compared with the labeled content. It was proved that the content determined in this experiment was basically consistent with the standard content in the sample, and the reproducibility was good. Therefore, this method can be used to determine the content of felodipine in drugs, and even the content of felodipine in different substances.

Sulfur dioxide adsorption by Iron Oxide Nanoparticles@Clinoptilolite/HCl

Introduction: The purpose of this study was to investigate and compare the effect of iron oxide nanoparticles on the adsorption of sulfur dioxide by modified zeolite with hydrochloric acid. In this investigation was used modi- fied zeolite with HCl with and without iron oxide nanoparticles (Iron Oxide Nanoparticles@Clinoptilolite/HCl) as adsorbent. Materials and methods: Structural characteristics, chemical composition and specific surface area of adsorbent were determined using the FTIR, FE- SEM, EDX, Mapping, XRD, XRF and BET techniques. Glass cylinder filled with zeolite seeds and SO2 cylinder balanced with N2 gas was used for experi- ments. It was evaluated factors affecting SO2 uptake process including tem- perature and contact time, also thermodynamics and kinetics of adsorption. Sulfur dioxide adsorption of real sample was taken with both adsorbents. Results: Adsorption efficiency of SO2 in the synthetic and actual sample were %82.8±5.5 and %67.2±7.21 respectively, by modified zeolite with HCl and iron oxide nanoparticles in the optimum conditions of temperature of 25 °C and duration 28.5 min. As well as, removal percentage average was obtained in the synthetic and actual sample %46.1±4.34 and %35.8±5.85 respectively, by modified zeolite with HCl without nanoparticles in optimum condition of temperature of 25 °C and contact time of 20.5 min.The results showed that SO2 adsorption is an exothermic and spontaneous process and adsorption ki- netics of sulfur dioxide by both adsorbent is more consistent Pseudo-second order kinetics model. Conclusion: The use of iron oxide nanoparticles on the zeolite can increase SO2 removal efficiency from the gas phase.

Principal’s Leadership Behaviours Influence on Teacher’s Job Satisfaction in Public Secondary Schools in Kenya

The purpose of the study was to establish the relationship between principal’s leadership behaviours and teacher’s job satisfaction in public secondary schools in Bungoma North Sub County, Bungoma County, Kenya. More specifically, the study sought to establish the relationship among four principal leadership behaviours: directive, participative, supportive and achievement oriented in relation to teacher job satisfaction. Path Goal model effectiveness formed the theoretical framework. Principal’s leadership behaviours formed the independent variable for the study while teacher’s job satisfaction, the dependent variable. The study adopted descriptive survey research approach. The unit sample of the study was all the 51 secondary schools in Bungoma North Sub County. The target population comprised of all the 51 principals and 761 teachers in all the 51 secondary schools in Bungoma North Sub County. All the 51 Principals were purposively selected from the sampled schools as they were leaders in those schools. The actual sample size of 263 teachers was selected purposively, making the actual sample size of the study to be 314 respondents. Data was collected using two sets of self-administered questionnaires. Spearman rho was used to determine the degree of relationship between principal’s leadership behaviours and teacher’s job satisfaction. The study concluded that directive, supportive, participative and achievement oriented leadership behaviours had a significant influence on teacher’s job satisfaction. Teachers also preferred directive leadership behaviours as opposed to principal’s achievement oriented leadership behaviours. The study recommended policy reforms on the action plans that influence job satisfaction of teachers

Perlukah menghitung ukuran sampel?

Sample size is an issue worth-considering but not the most essential thing to fulfil for a good research. A much more crucial cause of concern to any research is the validity of inference a research is drawing, i.e. the extent to which the research is able to control systematic error that stems from bias and confounding. Sample size refers to random error; it does not address nor correct systematic error. The larger sample size, the less random error, the more precise estimates a research can yield about difference/ association/ effect of a variable(s). Most of the assignment of values in any sample size formula is arbitrary. As such, the product of estimating sample size, regardless of the formula being used, cannot be viewed as an absolute end; the actual sample size can be larger or smaller than the estimated one. Beyond statistical aspect, several other important factors should be considered when estimating sample size, such as ethics, cost, and the amount oftime available for conducting the research.