***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: This brief article outlines some difficulties as well as benefits in conducting r and omized controlled trials  in social science setting s especially in developing countries . Some of the historical developments are summarized and certain applications in health sciences are discussed from method ological and policy st and points Methods for combining data from several studies exist and appear to be quite useful . None satisfactorily addresses the question of what studies should be combined . This issue is the most serious method ological limitation . Even studies with statistically significant interaction might still be combined if the effect were in the same direction . Thus , substantial scientific input is required as to what criteria must be met by each potential study . Much can be learned from combining or pooling data but it must be done cautiously . Pooling exercises do not replace well design ed prospect i ve clinical trials . Efforts for establishing basic design criteria to allow for multicentre and multicountry trials to be more easily combined might be useful . BACKGROUND Reducing the intakes of fats and increasing consumption of fruits and vegetables are an important goal for improving population health . Analyzing the effects of nutrition education programs on subjects ' dietary intakes incorporating factors such as habit persistence in diets , unhealthy eating habits , perceptions of health risks , participation motivation , and expectancies can yield useful insights . METHODS A Food Frequency Question naire ( FFQ ) was used to measure intakes at baseline , 6 and 12 months , by 318 and 548 postmenopausal women in , respectively , the Control and Intervention groups of the Women 's Health Trial : Feasibility Study in Minority Population s ( WHTFSMP ) . Information on background , behavioral , and anthropometric variables was collected . The Intervention group met in classes led by nutritionists . Dynamic r and om effects models were estimated for the two groups using the data at baseline , 6 and 12 months on the intakes of carbohydrate , saturated , monounsaturated , and polyunsaturated fats , fiber , beta-carotene , ascorbic acid , and calcium . RESULTS The nutrition education program lowered the intakes of fats while increasing fiber , beta-carotene , and ascorbic acid intakes especially in subjects scoring high on indices reflecting concerns about health , desirability of change , and participation motivation . In addition , subjects '  education was a predictor of dietary intakes in the Intervention group . CONCLUSIONS Nutrition education can be an effective tool for improving diets , but behavioral characteristics deserve greater attention in helping to design the most effective approaches for various target groups The increasing prevalence of obesity in the USA , especially among minority population s , is a serious public health concern . This present study analysed repeated measurements at baseline and at 6 and 12 months on 351 women in the control group and 575 women in the intervention group of the Women 's Health Trial : Feasibility Study in Minority Population s. Dynamic r and om effects models were estimated using the three repeated observations to explain the effects of energy and macronutrient intakes , physical exercise , unhealthy eating habits and socio-economic characteristics on the subjects ' body weights and waist and hip circumferences . In both the control and intervention groups , physical exercise was negatively associated with body weight and with waist and hip circumferences , while an index of unhealthy eating habits was positively associated ( P<0.05 ) . The proportion of energy derived from carbohydrate and from saturated and monounsaturated fat were often significant predictors of body weight and of waist and hip circumferences in the two groups . The results indicated that nutrition education programmes for improving eating habits and increasing physical exercise can reduce obesity prevalence in the USA This paper is the first of five papers in this issue that describes a new research consortium funded by the National Institutes of Health . It describes the design characteristics of the Childhood Obesity Prevention and Treatment Research ( COPTR ) trials and common measurements across the trials . The COPTR Consortium is conducting interventions to prevent obesity in pre-schoolers and treat overweight or obese 7 - 13 year olds . Four r and omized controlled trials will enroll a total of 1700 children and adolescents ( ~50 % female , 70 % minorities ) , and will test innovative multi-level and multi-component interventions in multiple setting s involving primary care physicians , parks and recreational centers , family advocates , and schools . For all the studies , the primary outcome measure is body mass index ; secondary outcomes , moderators and mediators of intervention include diet , physical activity , home and neighborhood influences , and psychosocial factors .  COPTR is being conducted collaboratively among four participating field centers , a coordinating center , and NIH project offices . Outcomes from COPTR have the potential to enhance our knowledge of interventions to prevent and treat childhood obesity Community-based interventions are , by their nature , tailored to the particular needs of the members and stakeholders of the community . In the area of safety promotion , the multifaceted aspects of violence and unintentional injuries necessitate complex intertwining of strategies and approaches . The evaluation of the effectiveness of any ‘ intervention ’ programme , either as a whole or of its discrete components , is thus challenging . In addition , st and ard experimental research design s involving controlled comparisons and the use of r and omisation are often not practical . The evaluation is complicated further when the numbers of events in the community that constitute outcomes to be measured , before and after the interventions , are small . This manuscript review s some of the statistical considerations that impact the evaluation of the effectiveness of such intervention approaches , and proposes a meta-regression methodology to address this complex issue . The application of the proposed methodology to the ‘ Safe Community ’ Model is provided as an example 
    Output:
    
Pooling may help to identify intervention components that may be more effective especially for subsets of participants with certain behavioral characteristics .
Pooling , when supported by statistical tests , can allow exploratory investigation of potential hypotheses and for the design of future interventions