The Role of Random Allocation in Randomized Controlled Trials: Distinguishing Selection Bias from Baseline Imbalance

Background: This paper addresses one threat to the internal validity of a randomized controlled trial (RCT), selection bias. Many authors argue that random allocation is used to ensure baseline equality between study conditions in a given study and that statistically significant differences at pretest mean that randomisation has failed.   Purpose: The purpose of this study was to clarify the role of random allocation in an RCT study. Is the role of random allocation to protect against selection bias? And does it have a further role, namely to ensure baseline equality and the absence of statistically significant differences between study conditions at pretest?   Setting: The participants for this study were 229 children in 1st and 2nd grade and data were collected as part of an RCT evaluation of a volunteer reading programme piloted in Ireland, Wizards of Words (WoW).   Intervention: Not applicable.   Research design: The allocation procedure adopted in this study was stratified and blocked random allocation.   Data collection and analysis: Data were collected using standardised and criterion-referenced tests of reading ability. Data were collected by qualified Speech and Language Therapists. Independent-samples t-tests were used to analyse pretest data.   Findings: The role of random allocation is to protect against selection bias, and statistically significant baseline differences can result even when random allocation has been successful. Whether or not random allocation has been successful is determined by the generation of the random allocation sequence and the steps taken to ensure its concealment. The size of differences between study conditions at pretest can be important for the analysis of posttest data but does not by itself determine whether random allocation was successful. In addition, there are serious concerns about the appropriateness of tests of significance when comparing two study conditions at pretest. Keywords: baseline equality; baseline imbalance; random allocation; selection bias; test of statistical significanc

Evaluation of the Restorative Practices Programme of the Childhood Development Initiative

This report presents the key findings of an independent evaluation, undertaken by the UNESCO Child and Family Research Centre at the National University of Ireland, Galway, of the Restorative Practice Programme, part of the Childhood Development Initiative's (CDI) Community Safety Initiative (CSI). The study comprises (i) a process study evaluation of programme implementation under the headings of programme utilisation, programme organisation and programme fidelity; and (ii) an outcomes study evaluation of programme impact on participants' work, lives, organisations and family, and also the wider impact on community building and collaborative action

Exploring the Utility of the Simple View of Reading in Irish Children Attending Schools in Areas Designated as Socially Disadvantaged

Evidence suggests that children living in areas designated as socially disadvantaged may be at risk for literacy difficulties. The Simple View of Reading (Gough & Tunmer, 1986; Hoover &Gough, 1986) is a theoretical model that sets out to describe the processes that children need to develop to become proficient readers, that is word recognition or decoding processes and language comprehension processes. The overall aim of this study was to investigate the utility of the Simple View of Reading in a cohort of Irish children attending schools designated as socially disadvantaged. The objectives were twofold. The first objective was to investigate predictors of reading accuracy, spelling and reading comprehension skills in this sample. The second objective was to investigate whether or not these predictors varied with age. The sample comprised fifty-nine children attending two schools. Inclusion criteria were: children between the ages of 5-8 years; a sample of children within three ranges of reading abilities as rated by their teachers (teachers were asked to rate the children’s reading ability as above average, average or below average); and a minimum score of 80 on the British Picture Vocabulary Scales (BPVS) (Dunn et al., 1997) to be included. Reading accuracy (single word reading and passage reading), reading comprehension, and spelling were measured using three standardised tests i.e., Weschler Individual Attainment Test 11UK, Teachers Version (WIAT, 11UK-T) (Weschler, 2006), the York Assessment of Reading for Comprehension (YARC) (Snowling et al., 2009), and the Single Word Spelling Test (SWST), (Sacre & Masterson, 2000). Potential predictors of literacy skills, such as phonemic awareness and phonic knowledge skills, were measured using criterion-referenced tests. Vocabulary was also a potential predictor and was measured using the BPVS. There was mixed evidence for the Simple View of Reading. While phonic knowledge, phonemic knowledge and non-word reading were predictors of reading, other factors such as vocabulary were also predictors. Although vocabulary was a predictor of reading comprehension for the total sample, the picture was less clear when the effect of age was explored. To conclude, there was mixed evidence to support the Simple View of Reading.  Nonetheless, the findings were encouraging in that children were acquiring literacy skills

The Role of Random Allocation in Randomized Controlled Trials: Distinguishing Selection Bias from Baseline Imbalance

Background: This paper addresses one threat to the internal validity of a randomized controlled trial (RCT), selection bias. Many authors argue that random allocation is used to ensure baseline equality between study conditions in a given study and that statistically significant differences at pretest mean that randomisation has failed.   Purpose: The purpose of this study was to clarify the role of random allocation in an RCT study. Is the role of random allocation to protect against selection bias? And does it have a further role, namely to ensure baseline equality and the absence of statistically significant differences between study conditions at pretest?   Setting: The participants for this study were 229 children in 1st and 2nd grade and data were collected as part of an RCT evaluation of a volunteer reading programme piloted in Ireland, Wizards of Words (WoW).   Intervention: Not applicable.   Research design: The allocation procedure adopted in this study was stratified and blocked random allocation.   Data collection and analysis: Data were collected using standardised and criterion-referenced tests of reading ability. Data were collected by qualified Speech and Language Therapists. Independent-samples t-tests were used to analyse pretest data.   Findings: The role of random allocation is to protect against selection bias, and statistically significant baseline differences can result even when random allocation has been successful. Whether or not random allocation has been successful is determined by the generation of the random allocation sequence and the steps taken to ensure its concealment. The size of differences between study conditions at pretest can be important for the analysis of posttest data but does not by itself determine whether random allocation was successful. In addition, there are serious concerns about the appropriateness of tests of significance when comparing two study conditions at pretest. Keywords: baseline equality; baseline imbalance; random allocation; selection bias; test of statistical significanc

Study of young carers in the Irish population. Full report.

The term ‘young carers’ refers to children and young people under the age of 18 whose lives are affected in some significant way by the care needs of another family or household member, and who provide care, or help to provide care, to that person. Traditionally, the focus of carer-orientated policy has been on adult carers. However, in the last 15 years there has been growing awareness of and interest in young carers. Research on this topic has greatly expanded and policy-makers and service providers are increasingly acknowledging the need for a specific policy response to address the needs of young carers and to provide support to them. The health problems of those with care needs, being cared for by young carers, included: • behavioural or learning difficulty; • combined intellectual and physical disability; • physical illness; • mental illness; • drug or alcohol addiction; • sensory impairmen