Cochrane

Introduction Most trials fail to recruit the number of participants they need within the time they had planned to conduct the study. Recruiting potential participants to research studies involves three stages: identifying, approaching and obtaining the consent of potential participants to join a study. Researchers often rely on healthcare staff, such ...

Background Survey questionnaires are important tools in public health and clinical research as they offer a convenient way of collecting data from a large number of respondents, dealing with sensitive topics, and are less resource intensive than other data collection techniques. The delivery of survey questionnaires via apps running on smartphones ...

A systematic review summarises evidence from multiple studies to answer a specific research question (e.g. what are the benefits and harms of a particular intervention for a particular health condition?). Often, there are many outcomes that systematic review authors could report to address their research question (e.g. pain, disability and quality of ...

Researchers and organizations often use evidence from randomized controlled trials (RCTs) to determine the efficacy of a treatment or intervention under ideal conditions, while studies of observational designs are used to measure the effectiveness of an intervention in non-experimental, 'real world' scenarios. Sometimes, the results of RCTs and observational ...

Background Most trials follow people up to collect data through personal contact after they have been recruited. Some trials get data from other sources, such as routine collected data or disease registers. There are many ways to collect data from people in trials, and these include using letters, the internet, telephone calls, text messaging, face-to-face ...

Random allocation to different groups to compare the effects of treatments is used in fair tests to find out which among the treatment options is preferable. Random allocation is only ethical, however, if there is genuine uncertainty about which of the treatment options is preferable. If a patient or their healthcare provider is certain which of the ...

This methodology review was conducted to assess the effects of different methods for obtaining unpublished studies (data) and missing data from studies to be included in systematic reviews. Six studies met the inclusion criteria, two were randomised studies and four were observational comparative studies evaluating different methods for obtaining missing ...

The non-reporting of a piece of research and the selective reporting of only some of its findings has been identified as a problem for research studies such as randomised trials and systematic reviews of these. If the decision about what to report and what to keep unpublished is based on the results obtained in the trial, this will lead to bias and ...

The validity of a systematic review depends on the methods used to conduct the review. If there is a systematic bias, such that studies with statistically significant or positive findings are more likely to be published and included in systematic reviews than trials with non-significant findings, then the validity of a review's conclusions can be threatened. This ...