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A Agresti

Publications and source records attributed to A Agresti.

At least 73 records · Page 4Linked to original sources
PubMedDate not supplied

Modelling ordered categorical data: recent advances and future challenges.

This article summarizes recent advances in the modelling of ordered categorical (ordinal) response variables. We begin by reviewing some models for ordinal data introduced in the literature in the past 25 years. We then survey recent extensions of these models and related methodology for special types of applications, such as for repeated measurement and other forms of clustering. We also survey other aspects of ordinal modelling, such as small-sample analyses, power and sample size considerations, and availability of software. Throughout, we suggest problem areas for future research and we highlight challenges for statisticians who deal with ordinal data.

Bayes Theorem↗
PubMedDate not supplied

A new model for ordinal pain data from a pharmaceutical study.

For the pain data analysed previously by Cox and Chuang, this paper proposes a new model that assumes monotone scores for ordered response categories. This proposed model possesses several attractive features and allows a stochastic ordering of the drugs under comparison. Such a model also provides insight regarding the ordinal scale used to classify response. Estimation of the parameters in the model is obtained by use of BMDP3R.

Analgesics↗
PubMedDate not supplied

Exact inference for categorical data: recent advances and continuing controversies.

Methods for exact small-sample analyses with categorical data have been increasingly well developed in recent years. A variety of exact methods exist, primarily using the approach that eliminates unknown parameters by conditioning on their sufficient statistics. In addition, a variety of algorithms now exist for implementing the methods. This paper briefly summarizes the exact approaches and describes recent developments. Controversy continues about the appropriateness of some exact methods, primarily relating to their conservative nature because of discreteness. This issue is examined for two simple problems in which discreteness can be severe--interval estimation of a proportion and the odds ratio. In general, adjusted exact methods based on the mid-P-value seem a reasonable way of reducing the severity of this problem.

Data Interpretation, Statistical↗
PubMedDate not supplied

Analysis of gamma4 germline transcription in human B cells.

BACKGROUND: Allergic reactions occur rarely in patients with chronic helminth infections, although FcepsilonRI-bearing cells are sensitized with anti-parasite IgE and are exposed to antigen. The inhibition of allergic reactivity is due to 'blocking antibodies', predominantly IgG4. IgG4 antibodies represent 50-95% of anti-filarial IgG, and have blocking activity because they compete with cell-bound IgE for allergen binding. Blocking IgG4 antibodies have also been detected in patients treated with immunotherapy. However, the molecular mechanisms of IgG4 regulation have remained unexplored. We address this issue starting with the IL-4-dependent induction of gamma4 germline transcription, an essential step in the commitment to isotype switching. RESULTS: gamma4 germline transcripts were cloned and shown to contain Igamma4 spliced to the 5' portion of Cgamma4 using the splice donor site shared by gamma1 and gamma3 germline transcripts. Sequence analysis located the human Igamma4 exon thick approximate0.6 kb upstream of the Sgamma4 region. Four major transcription start sites located 547-583 bp upstream of the Igamma4 splice donor site were identified by primer extension analysis. A HindIII/NaeI construct (-413/+466) had the highest activity in reporter assays. Transcription was induced 4.6-fold by IL-4, 2.1-fold by CD40 engagement, and 14.5-fold by a combination of the two signals. Thus CD40 crosslinking enhanced IL-4-dependent transcription by 3.1-fold, showing that the two stimuli act synergistically. CONCLUSION: As we understand more about IgG4 regulation, our hope is to apply to allergy the lesson we learnt from helminth infections.

Antibodies, Blocking↗