Estimation of Heterogeneous and Nonstationary Retail Demand with Aggregate Data

2021 ◽  
Author(s):  
Yihui Huang ◽  
Chen Wang ◽  
Lei Zhao ◽  
Jan C. Fransoo
Keyword(s):  
Aggregate Data ◽  
Retail Demand

Patronage of urban commercial clusters: A network-based extension of the Huff model for balancing location and size

2017 ◽  
Vol 45 (3) ◽  
pp. 508-528 ◽  
Author(s):  
Andres Sevtsuk ◽  
Raul Kalvo
Keyword(s):  
Spatial Configuration ◽  
Analysis Tool ◽  
Spatial Networks ◽  
Urban Network ◽  
Household Level ◽  
New Town ◽  
New Towns ◽  
Public Facilities ◽  
User Access ◽  
Retail Demand

We introduce a version of the Huff retail expenditure model, where retail demand depends on households’ access to retail centers. Household-level survey data suggest that total retail visits in a system of retail centers depends on the relative location pattern of stores and customers. This dependence opens up an important question—could overall visits to retail centers be increased with a more efficient spatial configuration of centers in planned new towns? To answer this question, we implement the model as an Urban Network Analysis tool in Rhinoceros 3D, where facility patronage can be analyzed along spatial networks and apply it in the context of the Punggol New Town in Singapore. Using fixed household locations, we first test how estimated store visits are affected by the assumption of whether shoppers come from homes or visit shops en route to local public transit stations. We then explore how adjusting both the locations and sizes of commercial centers can maximize overall visits, using automated simulations to test a large number of scenarios. The results show that location and size adjustments to already planned retail centers in a town can yield a 10% increase in estimated store visits. The methodology and tools developed for this analysis can be extended to other context for planning and right-sizing retail developments and other public facilities so as to maximize both user access and facilities usage.

scholarly journals Comparing the use of aggregate data and various methods of integrating individual patient data to network meta-analysis and its application to first-line ART

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Steve Kanters ◽  
Mohammad Ehsanul Karim ◽  
Kristian Thorlund ◽  
Aslam H. Anis ◽  
Michael Zoratti ◽  
...  
Keyword(s):  
Meta Analysis ◽  
Evidence Base ◽  
Aggregate Data ◽  
World Health ◽  
Coefficient Estimates ◽  
Two Stage ◽  
Individual Patient Level ◽  
One Stage ◽  
Meta Regression ◽  
Empirical Priors

Abstract Background The 2018 World Health Organization HIV guidelines were based on the results of a network meta-analysis (NMA) of published trials. This study employed individual patient-level data (IPD) and aggregate data (AgD) and meta-regression methods to assess the evidence supporting the WHO recommendations and whether they needed any refinements. Methods Access to IPD from three trials was granted through ClinicalStudyDataRequest.com (CSDR). Seven modelling approaches were applied and compared: 1) Unadjusted AgD network meta-analysis (NMA) – the original analysis; 2) AgD-NMA with meta-regression; 3) Two-stage IPD-AgD NMA; 4) Unadjusted one-stage IPD-AgD NMA; 5) One-stage IPD-AgD NMA with meta-regression (one-stage approach); 6) Two-stage IPD-AgD NMA with empirical-priors (empirical-priors approach); 7) Hierarchical meta-regression IPD-AgD NMA (HMR approach). The first two were the models used previously. Models were compared with respect to effect estimates, changes in the effect estimates, coefficient estimates, DIC and model fit, rankings and between-study heterogeneity. Results IPD were available for 2160 patients, representing 6.5% of the evidence base and 3 of 24 edges. The aspect of the model affected by the choice of modeling appeared to differ across outcomes. HMR consistently generated larger intervals, often with credible intervals (CrI) containing the null value. Discontinuations due to adverse events and viral suppression at 96 weeks were the only two outcomes for which the unadjusted AgD NMA would not be selected. For the first, the selected model shifted the principal comparison of interest from an odds ratio of 0.28 (95% CrI: 10.17, 0.44) to 0.37 (95% CrI: 0.23, 0.58). Throughout all outcomes, the regression estimates differed substantially between AgD and IPD methods, with the latter being more often larger in magnitude and statistically significant. Conclusions Overall, the use of IPD often impacted the coefficient estimates, but not sufficiently as to necessitate altering the final recommendations of the 2018 WHO Guidelines. Future work should examine the features of a network where adjustments will have an impact, such as how much IPD is required in a given size of network.

scholarly journals Characteristics of intracerebral haemorrhage associated with COVID-19: a systematic review and pooled analysis of individual patient and aggregate data

2021 ◽  
Author(s):  
R. Beyrouti ◽  
J. G. Best ◽  
A. Chandratheva ◽  
R. J. Perry ◽  
D. J. Werring
Keyword(s):  
Intracerebral Haemorrhage ◽  
Pooled Analysis ◽  
Aggregate Data ◽  
High Rate ◽  
Individual Data ◽  
Aggregate Level ◽  
Level Data ◽  
Pooled Prevalence ◽  
Underlying Mechanisms ◽  
Different Characteristics

Abstract Background and purpose There are very few studies of the characteristics and causes of ICH in COVID-19, yet such data are essential to guide clinicians in clinical management, including challenging anticoagulation decisions. We aimed to describe the characteristics of spontaneous symptomatic intracerebral haemorrhage (ICH) associated with COVID-19. Methods We systematically searched PubMed, Embase and the Cochrane Central Database for data from patients with SARS-CoV-2 detected prior to or within 7 days after symptomatic ICH. We did a pooled analysis of individual patient data, then combined data from this pooled analysis with aggregate-level data. Results We included data from 139 patients (98 with individual data and 41 with aggregate-level data). In our pooled individual data analysis, the median age (IQR) was 60 (53–67) years and 64% (95% CI 54–73.7%) were male; 79% (95% CI 70.0–86.9%) had critically severe COVID-19. The pooled prevalence of lobar ICH was 67% (95% CI 56.3–76.0%), and of multifocal ICH was 36% (95% CI 26.4–47.0%). 71% (95% CI 61.0–80.4%) of patients were treated with anticoagulation (58% (95% CI 48–67.8%) therapeutic). The median NIHSS was 28 (IQR 15–28); mortality was 54% (95% CI 43.7–64.2%). Our combined analysis of individual and aggregate data showed similar findings. The pooled incidence of ICH across 12 cohort studies of inpatients with COVID-19 (n = 63,390) was 0.38% (95% CI 0.22–0.58%). Conclusions Our data suggest that ICH associated with COVID-19 has different characteristics compared to ICH not associated with COVID-19, including frequent lobar location and multifocality, a high rate of anticoagulation, and high mortality. These observations suggest different underlying mechanisms of ICH in COVID-19 with potential implications for clinical treatment and trials.

A Tactical Error in the Analysis of Tactical Voting: A Response to Niemi, Whitten and Franklin

1993 ◽  
Vol 23 (1) ◽  
pp. 131-137 ◽  
Author(s):  
Geoffrey Evans ◽  
Anthony Heath
Keyword(s):  
Aggregate Data ◽  
Individual Characteristics ◽  
General Election ◽  
The Other ◽  
Valid Measure ◽  
Major Party

In their article ‘Constituency Characteristics, Individual Characteristics and Tactical Voting in the 1987 British General Election’, Niemi, Whitten and Franklin claim that in the 1987 general election ‘about one in every six voters … had tactical considerations in mind in deciding whom to vote for’. As they point out, this figure is far higher than Heath et al.'s estimate of 6.5 per cent of major party voters having ‘a tactical motivation for their vote’. It is also far higher than estimates obtained by other analyses of the 1987 election using aggregate data. In this Note we point to methodological weaknesses in Niemi, Whitten and Franklin's article which indicate that their estimate is unlikely to be a valid measure of tactical voting, at least of the concept as customarily understood by political scientists. Indeed, when looked at carefully, the evidence they present to support their expanded estimate of tactical voting serves only to re-affirm the original claims of Heath and his colleagues and the other conservative estimates of the prevalence of tactical voting.

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