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About 943 papers for “Restricted randomization”

Restricted randomization

R. A. Bailey · Biometrika · 1983

A method of restricted randomization is given suitable for any block structure in which the number of levels of each block factor is a prime power. Under the assumption that all blocks are linear, certain patterns are designated undesirable, and initial arrangements are found which, if used in conjunction with the method of restricted randomization advocated, ensure that no undesirable patterns occur.

Cited by 29

Restricted Randomization

R. A. Bailey · Biometrika · 1983

A method of restricted randomization is given suitable for any block structure in which the number of levels of each block factor is a prime power. Under the assumption that all blocks are linear, certain patterns are designated undesirable, and initial arrangements are found which, if used in conjunction with the method of restricted randomization advocated, ensure that no undesirable patterns occur.

Cited by 2

Restricted Randomization versus Blocking

R. A. Bailey · International Statistical Review · 1985

La randomisation restreinte peut etre superieure a l'utilisation de blocs artificiels quand on dispose de peu de parcelles. On presente de bonnes methodes de randomisation restreinte pour 2 ou 4 objets repartis en 8 parcelles constituant un rectangle 2×4

Cited by 11

Restricted Randomization: Pros and Cautions

Jonathan Chipman · 2017

This chapter looks back to the foundation of randomization and ties together modern-day randomization approaches and considerations. Randomization removes, on average, the effect of any bias upon the experiment’s conclusions. Yet, in a single randomization, nontrivial imbalances in factors related to the outcome (i.e. confounders) can be common, and rare randomizations can fail dramatically. Restrictions to randomization help diminish the risk of rare, bad randomizations and can increase the efficiency of the experiment to detect the effect of an experimental condition, if one truly exists. The emphasis of this chapter is to understand the context of randomization, bring awareness of pros and cautions of various randomization schemes, and encourage covariate-adjusted randomization in experiments where experimental units are randomized sequentially. There is a wealth of additional literature on randomized trials where experimental units are all known before randomization and on covariate-adjusted response-adaptive randomization, though these topics are beyond the scope of this chapter.

Cited by 0

Significance tests with Restricted Randomization Design

R. T. Smythe, L. J. Wei · Biometrika · 1983

Experimental subjects are assigned to one of two treatments sequentially by restricted randomization assignment rules. Significance tests generated from these rules are discussed. Under rather mild conditions on the test scores the asymptotic null permutational distribution of tests based on the urn design (Wei, 1977, 1978a) is shown to be normal.

Cited by 0

Conditional Inference for Restricted Randomization Designs

R. T. Smythe · The Annals of Statistics · 1988

In a clinical trial to compare two treatments, suppose that patients are assigned to treatment according to a certain class of restricted randomization rules. Conditional on the difference in numbers between the two treatment groups, the asymptotic null distribution of a class of permutation tests is shown to be Gaussian.

Cited by 10Open access

Interval estimation with restricted randomization rules

Lee‐Jen Wei, R. T. Smythe, Cyrus R. Mehta · Biometrika · 1989

In comparing two treatments in a clinical trial, suppose that patients are assigned sequentially to treatments by a restricted randomization rule. Exact and approximate confidence intervals for treatment difference are derived without assuming that the study subjects were obtained by random sampling from a well-defined population. We show that, if there is a time trend among the responses of study subjects, one should not ignore the design in the analysis. All the procedures are illustrated with a real-life example.

Cited by 1

Modeling the effects of restricted randomization

Johnston, Robert S. · Library and Archives Canada (Government of Canada) · 1998

Because the usual linear model does not convey information pertinent to the randomization process, the linear model and associated expected mean squares are inadequate when randomization is restricted in some way. The linear model is extended to incorporate such information by viewing the realized observations as a fraction of the potential observations, and utilizing the idea of bias or aliasing in a manner similar to fractional designs. In particular, two areas of restricted randomization are examined (1) restricting the run-order of a sequential experiment and (2) restrictions resulting from inherent structure of the experimental material (blocking). In both cases treatment effects and effects associated with the randomization process may be non-additive, in contrast to some of the previous work that has assumed such effects are additive. In addition, the nature of the resulting bias is examined. Rules are specified that allow construction of pseudo expected mean squares that indicate the presence of bias that results from restricting the randomization process.

Cited by 0

Restricted Randomization Designs in Clinical Trials

Richard Simon · Biometrics · 1979

Though therapeutic clinical trials are often categorized as using either "randomization" or "historical controls" as a basis for treatment evaluation, pure random assignment of treatments is rarely employed. Instead various restricted randomization designs are used. The restrictions include the balancing of treatment assignments over time and the stratification of the assignment with regard to covariates that may affect response. Restricted randomization designs for clinical trials differ from those of other experimental areas because patients arrive sequentially and a balanced design cannot be ensured. The major restricted randomization designs and arguments concerning the proper role of stratification are reviewed here. The effect of randomization restrictions on the validity of significance tests is discussed.

Cited by 176

Some Restricted randomization rules in sequential designs

José Francisco Soares, Changbao Wu · Communication in Statistics- Theory and Methods · 1983

This paper presents a new class of designs (Big Stick Designs) for sequentially assigning experimental units to treatments, when only the time covariate is considered. By prescribing the degree of imbalance which the experimenters can tolerate, complete randomization is used as long as the imbalance of the treatment allocation does not exceed the prescribed value. Once it reaches the value, a deterministic assignment is made to lower the imbalance. Such designs can be easily implemented with no programming and little personnel support. They compare favorably with the Biased Coin Designs, the Permuted Black Designs, and the Urn Designs, as far as the accidental bias and selection bias are concerned. Generalizations of these designs are considered to achieve various purposes, e.g., avoidance of deterministic assignments, early balance, etc.

Cited by 167