One and Two Restrictions on Randomization
Daryl S. Paulson in Applied Statistical Designs for the Researcher, 2003
The randomized complete block design is different from a completely randomized design. Instead of randomly selecting each sample unit from all the N observations, randomization is conducted within the specific test group samples. This design is very useful when experimental units can be grouped meaningfully. Such a grouping is designated a block. The objective of blocking is to have the within-block units as uniform as possible. This is not a new concept, for we encountered it in pairing in Chap. 4 for the matched paired t-tests. Variability among the sample units in different blocks will be greater, on the average, than variability among the units in the same block. Ideally, the variability among experimental units is controlled so that the variation among blocks is maximized and the variability within minimized.
Randomization and Bias in Historical Perspective
Vance W. Berger in Randomization, Masking, and Allocation Concealment, 2017
But randomization is not synonymous with arbitrary; there still should be a “structure” to ensure that the intervention and the control groups are comparable—for example, that they have the same number of members. Equal group size is not assured with a completely random sequence (a fair coin can come up heads successively after several tosses by chance). Historically, one way to deal with this issue has been to employ permuted block design. According to this strategy, patients are assigned to the treatment or control arm in blocks (e.g., of four patients, six patients, etc.), and each block will be a different possible permutation of the ways that the two or more interventions could be sequenced. Within each block, however, an equal number of patients will be assigned to each trial arm. By randomly selecting a different permutation of the block design when one block has been completed, researchers are attempting to achieve both variability (from block to block) and order (equal assignment).
Evaluating Performance Benefits of Conditioning Formulations on Human Skin
Randy Schueller, Perry Romanowski in Conditioning Agents for Hair and Skin, 2020
A modest increase in cell turnover is thought to improve the health of the skin by helping to remove dull, skin surface cells (29). Compounds such as retinoids, alpha-hydroxy acids, and beta-hydroxy acids all have keratolytic activity, and they are commonly used in today's antiaging products because of their effects on cell turnover, but also because they are beneficial in improving the photoaging attributes discussed in Section III.C.l. Fluorescent staining of the stratum corneum (SC) with dansyl chloride has been shown to be an effective method for estimating SC replacement time (30). Approximately 18 to 20 subjects are used to do pairwise comparisons on the volar forearm (see Section III.A). This allows one arm to be treated with the test product, and the contralateral arm to be treated with a placebo control or no treatment. Testing multiple test products requires a balanced block design with additional subjects.
Type-I intermittency from Markov binary block visibility graph perspective
Published in Journal of Applied Statistics, 2021
Pejman Bordbar, Sodeif Ahadpour
In this section, we demonstrate the binary block design in order to optimize the Markov binary visibility graph to analyze laminar and chaotic zones in the type-I intermittency. The block design is a topic in combinatorial mathematics which can be used in all or part of methods and also for algorithms of taxonomy in order to boost classifications of various phenomena in applied sciences [6,29]. A block design is the type of experimental design which 7]. A block design is binary if all of arrays 7]. In the other words, if each treatment occurs at most once in a block, the design is a Binary Block Design (BBD) [4]. The BBD has more applications in pure and applied Sciences [12–14].
Does Music Matter? A Look at the Issues and the Evidence
Published in Developmental Neuropsychology, 2019
With these considerations in mind, we begin our review of studies, correlational and experimental, of the effects of music training on spatial performance. Several are by Rauscher herself. In one, 3- and 4-year-olds, after 6–8 months of individual piano lessons, scored 34% higher on the Object Assembly subtest from the Wechsler Preschool and Primary Scale of Intelligence-Revised (Wechsler, 1989) than children given computer or singing lessons or no training (Rauscher et al., 1997). The test was given 24 hours after training, which means that the effects lasted at a minimum far longer than the 10–15 minutes in Rauscher et al. (1993) listening study. No differences, however, were found on Block Design and Geometric Design. In a second study, with group lessons, 32 kindergarten children who, for 4 months, had twice-weekly 20-minute-long piano lessons scored higher on two spatial tests, Block Building and Puzzle Block (arranging puzzle pieces to create a familiar object), than 28 children with no lessons, and scored even higher after 4 more months of lessons (Rauscher & Zupan, 2000). This was one of the studies that compared the sexes and found no differences (see endnote 15).
Perceived stress among Hispanic young adults: Impact of the coping with work and family stress program
Published in Journal of American College Health, 2023
Marivic B. Torregosa, Marcus Antonius Ynalvez, Maria del Rosario Benavides, Nandita Chaudhuri, Christopher Craddock
This study was conducted from September 2015 through September 2018 after obtaining Institutional Review Board (IRB) approval. The study was a three-year project designed to prevent substance abuse, HIV infection, and hepatitis C infection among young adult Hispanics through an evidence-based stress intervention. IRB approval was obtained from the implementing institution. Hispanic college students aged 18–24 were recruited from a Hispanic-serving institution located in a U.S. southern border city. A permuted block design with repeated measures was used in this study. Participants were randomly assigned to treatment and control groups. The treatment group received the CWFS evidence-based curriculum aimed at reducing perceived stress while the control group did not receive any programming. The CWFS consisting of 12 modules was delivered to the treatment group. One module per week lasting 90 min per session was delivered to small groups of 15–20 participants by trained interventionists or facilitators. The frequency of the intervention delivery was later changed into two modules per week in order to contain the intervention delivery within the regular academic semester. Such change impacted cohorts 2–9.
Related Knowledge Centers
- Design of Experiments
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