OBJECTIVES: In large-scale field trials, randomization by cluster is frequently used because of the administrative convenience, a desire to reduce the effect of treatment contamination, and the need to avoid ethical issues that might otherwise arise. Cluster randomization trials are experiments in which intact social unit, e.g., families, schools, cities, rather than independent individuals are randomly allocated to intervention groups. The positive correlation among responses of subjects from the same cluster is in matter in cluster randomization. This thesis is to compare the results of three randomization methods by standard error of estimator of treatment effect. METHODS: We simulated cholesterol data varing the size of the cluster and the level of the correlation in clusters and analyzed the effect of cholesterol-lowering agent. RESULTS: In intra-cluster randomization the standard error of the estimator of treatment effect is smallest relative to that in inter-cluster randomization and that in individual randomization. CONCLUSIONS: Intra-cluster randomization is the most efficient in its standard error of estimator of treatment effect but other factor should be considered when selecting a specific randomization method.
Cholesterol ; Ethics ; Humans ; Random Allocation*

Establishing the significance of observed effects is a preliminary requirement for any meaningful interpretation of clinical and experimental Electroencephalography or Magnetoencephalography (MEG) data. We propose a method to evaluate significance on the level of sensors whilst retaining full temporal or spectral resolution. Input data are multiple realizations of sensor data. In this context, multiple realizations may be the individual epochs obtained in an evoked-response experiment, or group study data, possibly averaged within subject and event type, or spontaneous events such as spikes of different types. In this contribution, we apply Statistical non-Parametric Mapping (SnPM) to MEG sensor data. SnPM is a non-parametric permutation or randomization test that is assumption-free regarding distributional properties of the underlying data. The method, referred to as Maps SnPM, is demonstrated using MEG data from an auditory mismatch negativity paradigm with one frequent and two rare stimuli and validated by comparison with Topographic Analysis of Variance (TANOVA). The result is a time- or frequency-resolved breakdown of sensors that show consistent activity within and/or differ significantly between event or spike types. TANOVA and Maps SnPM were applied to the individual epochs obtained in an evoked-response experiment. The TANOVA analysis established data plausibility and identified latencies-of-interest for further analysis. Maps SnPM, in addition to the above, identified sensors of significantly different activity between stimulus types.
Electroencephalography ; Magnetoencephalography ; Methods ; Random Allocation

In a large number of randomized controlled trials, researchers provide P values for demographic data, which are commonly reported in table 1 of the article for the purpose of emphasizing the lack of differences between or among groups. As such, the authors intend to demonstrate that statistically insignificant P values in the demographic data confirm that group randomization was adequately performed. However, statistically insignificant P values do not necessarily reflect successful randomization. It is more important to rigorously establish a plan for statistical analysis during the design and planning stage of the study, and to consider whether any of the variables included in the demographic data could potentially affect the research results. If a researcher rigorously designed and planned a study, and performed it accordingly, the conclusions drawn from the results would not be influenced by P values, regardless of whether they were significant. In contrasts, imbalanced variables could affect the results after variance controlling, even though whole study process are well planned and executed. In this situation, the researcher can provide results with both the initial method and a second stage of analysis including such variables. Otherwise, for brief conclusions, it would be pointless to report P values in a table simply listing baseline data of the participants.
Bias (Epidemiology) ; Methods ; Random Allocation

OBJECTIVEComparing the dental handpiece' s cleaning effect between manual cleaning and machine cleaning.

METHODSEighty same contaminated dental handpieces were randomly divided into experimental group and control group, each group contains 40 pieces. The experimental group was treated by full automatic washing machine, and the control group was cleaned manually. The cleaning method was conducted according to the operations process standard, then ATP bioluminescence was used to test the cleaning results.

RESULTSAverage relative light units (RLU) by ATP bioluminescence detection were as follows: Experimental group was 9, control group was 41. The two groups were less than the recommended RLU value provided by the instrument manufacturer (RLU < or = 45). There was significant difference between the two groups (P < 0.05).

CONCLUSIONThe cleaning quality of the experimental group was better than that of control group. It is recommended that the central sterile supply department should clean dental handpieces by machine to ensure the cleaning effect and maintain the quality.

A pilot study asks whether something can be done, should the researchers proceed with it, and if so, how. However, a pilot study also has a specific design feature; it is conducted on a smaller scale than the main or full-scale study. In other words, the pilot study is important for improvement of the quality and efficiency of the main study. In addition, it is conducted in order to assess the safety of treatment or interventions and recruitment potentials, examine the randomization and blinding process, increase the researchers' experience with the study methods or medicine and interventions, and provide estimates for sample size calculation. This review discusses with a focus on the misconceptions and the ethical aspect of a pilot study. Additionally how to interpret the results of a pilot study is also introduced in this review.
Pilot Projects* ; Random Allocation ; Sample Size

Random allocation is commonly used in medical researches, and has become an essential part of designing clinical trials. It produces comparable groups with regard to known or unknown prognostic factors, and prevents the selection bias which occurs due to the arbitrary assignment of subjects to groups. It also provides the background for statistical testing. Depending on the change in allocation probability, random allocation is divided into two categories: fixed allocation randomization and dynamic allocation randomization. In this paper, the author briefly introduces both the theory and practice of randomization. The definition, necessity, principal, significance, and classification of randomization are also explained. Advantages and disadvantages of each randomization technique are further discussed. Dynamic allocation randomization (Adaptive randomization), which is as yet unfamiliar with the anesthesiologist, is also introduced. Lastly, the methods and procedures for random sequence generation using Microsoft Excel is provided.
Classification ; Random Allocation* ; Research Design ; Selection Bias

Random allocation is commonly used in medical researches, and has become an essential part of designing clinical trials. It produces comparable groups with regard to known or unknown prognostic factors, and prevents the selection bias which occurs due to the arbitrary assignment of subjects to groups. It also provides the background for statistical testing. Depending on the change in allocation probability, random allocation is divided into two categories: fixed allocation randomization and dynamic allocation randomization. In this paper, the author briefly introduces both the theory and practice of randomization. The definition, necessity, principal, significance, and classification of randomization are also explained. Advantages and disadvantages of each randomization technique are further discussed. Dynamic allocation randomization (Adaptive randomization), which is as yet unfamiliar with the anesthesiologist, is also introduced. Lastly, the methods and procedures for random sequence generation using Microsoft Excel is provided.
Classification ; Random Allocation* ; Research Design ; Selection Bias

To study the effects of different pH HEPES-KH reperfusate solution on immature myocardial protection, isolated perfused Langendorff model from immature rabbit hearts were developed formed. Control group (C) was perfused only with pH 7.4 HEPES-KH solution for 90 min. Ischemia/reperfusion group (group I/R) was perfused with pH 7.4 HEPES-KH solution before ischemia or after ischemia. Experimental group (group E), after ischemia, was perfused with pH 6.8, pH 7.1 and pH 7.4 HEPES-KH solutions for 5 min, 5 min, and 20 min, respectively. The left ventricular function recovery, MWC, LDH and CK leakage, MDA, ATP content, and SOD activity were determined. Our results showed that the left ventricular function recovery, ATP content and SOD activity in group E were higher than those of group I/R (P < 0.05). MWC, MDA content, LDH and CK leakage in group E were lower than those of group I/R (P < 0.05). These findings suggested that pH paradox might be one of important mechanisms for immature myocardial ischemia-reperfusion injury, and acidic perfusate, at the beginning of reperfusion, might attenuate pH paradox and ameliorate functional recovery in isolated perfused immature rabbit hearts.
Myocardium/metabolism ; Random Allocation ; Superoxide Dismutase/metabolism

BACKGROUND AND PURPOSE: Mechanical thrombectomy with or without intravenous thrombolysis is indicated in the acute treatment of ischemic strokes caused by an emergent large-vessel occlusion (ELVO) within 6 hours from symptom onset. However, a significant proportion of patients are referred to comprehensive stroke centers beyond this therapeutic time window. This study performed a pooled analysis of data from trials in which mechanical thrombectomy was performed beyond 6 hours from symptom onset. METHODS: We searched for randomized controlled trials that compared mechanical thrombectomy with the best medical treatment beyond 6 hours for ischemic strokes due to ELVO and reported on between 1990 and April 2018. The intervention group comprised patients treated with mechanical thrombectomy. Statistical analysis was conducted while pooling data and analyzing fixed- or random-effects models as appropriate. RESULTS: Four trials involving 518 stroke patients met the eligibility criteria. There were 267 strokes treated with mechanical thrombectomy, with a median time of 10.8 hours between when the patient was last known to be well to randomization. We observed a significant difference between groups concerning the rate of functional independence at 90 days from stroke, with an absolute difference of 27.5% (odds ratio=3.33, 95% CI=1.81–6.12, p < 0.001) and good recanalization (odds ratio=13.17, 95% CI=4.17–41.60, p < 0.001) favoring the intervention group. CONCLUSIONS: This meta-analysis confirms the efficacy of mechanical thrombectomy in selected ischemic stroke patients beyond 6 hours from symptom onset. The selection is mainly based on the limited core infarct detected by emergent assessment using neuroimaging techniques.
Humans ; Neuroimaging ; Random Allocation ; Stroke* ; Thrombectomy*

OBJECTIVETo evaluate the effect of repeated sintering on the color and translucency of dental lithium disilicate-based glass ceramic.

METHODSThirty disc specimens (10 mm in diameter, and 1.00 mm ± 0.01 mm in thickness) were fabricated using an IPS e.max Press HT A2 ingot and then randomly divided into six groups (SO, S1, S2, S3, S4, and S5) (n = 5). Each group was sintered 0, 1, 2, 3, 4, and 5 times individually according to the manufacturer's recommendation. After polishing, ultrasonic cleaning, and drying, the color parameters (L*, a*, and b* values) and transmittance (τ) of all the specimens were measured using a ShadeEye NCC dental colorimeter and a TM-2 spectrophotometer, respectively. Subsequently, C*ab and ΔE were calculated. The results were statistically analyzed using SPSS 17.0 software for ANOVA and LSD.

RESULTSAfter repeated sintering, the L* value significantly decreased (P < 0.05), and the a*, b*, and C*ab values initially increased and then decreased (P < 0.05). The color parameters (L*, a*, and b*) and the C*ab values of group S3 were higher than those of the other groups. The τ values initially increased and then decreased (P < 0.05), and these values were optimal when sintered twice. In terms of transmittance (τ), statistical differences existed between the following groups: S0 and S2, S0 and S3,.S2 and S5, and S3 and S5 (P < 0.05). Compared with group S0, the color differences ΔE were 0.89 minimally and 2.01 maximally after different sintering times, which can be clinically acceptable.

CONCLUSIONRepeated sintering can affect the color and translucency of the IPS e.max Press lithium disilicate-based glass ceramic, but the color difference can be clinically acceptable.