Fast Polyhedral Adaptive Conjoint Estimation

We propose and test a new adaptive conjoint analysis method that draws on recent polyhedral “interior-point” developments in mathematical programming. The method is designed to offer accurate estimates after relatively few questions in problems involving many parameters. Each respondent’s ques-tions are adapted based upon prior answers by that respondent. The method requires computer support but can operate in both Internet and off-line environments with no noticeable delay between questions. We use Monte Carlo simulations to compare the performance of the method against a broad array of relevant benchmarks. While no method dominates in all situations, polyhedral algorithms appear to hold significant potential when (a) metric profile comparisons are more accurate than the self-explicated importance measures used in benchmark methods, (b) when respondent wear out is a concern, and (c) when product development and/or marketing teams wish to screen many features quickly. We also test hybrid methods that combine polyhedral algorithms with existing conjoint analysis methods. We close with suggestions on how polyhedral methods can be used to address other marketing problems.Sloan School of Management and the Center for Innovation in Product Development at MI

Application and Test of Web-based Adaptive Polyhedral Conjoint Analysis

In response to the need for more rapid and iterative feedback on customer preferences, researchers are developing new web-based conjoint analysis methods that adapt the design of conjoint questions based on a respondent’s answers to previous questions. Adapting within a respondent is a difficult dy-namic optimization problem and until recently adaptive conjoint analysis (ACA) was the dominant method available for addressing this adaptation. In this paper we apply and test a new polyhedral method that uses “interior-point” math programming techniques. This method is benchmarked against both ACA and an efficient non-adaptive design (Fixed). Over 300 respondents were randomly assigned to different experimental conditions and were asked to complete a web-based conjoint exercise. The conditions varied based on the design of the con-joint exercise. Respondents in one group completed a conjoint exercise designed using the ACA method, respondents in another group completed an exercise designed using the Fixed method, and the remaining respondents completed an exercise designed using the polyhedral method. Following the conjoint exer-cise respondents were given $100 and allowed to make a purchase from a Pareto choice set of five new-to-the-market laptop computer bags. The respondents received their chosen bag together with the differ-ence in cash between the price of their chosen bag and the$100. We compare the methods on both internal and external validity. Internal validity is evaluated by comparing how well the different conjoint methods predict several holdout conjoint questions. External validity is evaluated by comparing how well the conjoint methods predict the respondents’ selections from the choice sets of five bags. The results reveal a remarkable level of consistency across the two validation tasks. The polyhe-dral method was consistently more accurate than both the ACA and Fixed methods. However, even better performance was achieved by combining (post hoc) different components of each method to create a range of hybrid methods. Additional analyses evaluate the robustness of the predictions and explore al-ternative estimation methods such as Hierarchical Bayes. At the time of the test, the bags were proto-types. Based, in part, on the results of this study these bags are now commercially available.The Sloan School of Management, the Center for Innovation in Product Development at MIT and the EBusiness Center at MI

Measuring Consumer Preferences Using Conjoint Poker

We develop and test an incentive-compatible Conjoint Poker (CP) game. The preference data collected in the context of this game are comparable to incentive-compatible choice-based conjoint (CBC) analysis data. We develop a statistical efficiency measure and an algorithm to construct efficient CP designs. We compare incentive-compatible CP to incentive-compatible CBC in a series of three experiments (one online study and two eye-tracking studies). Our results suggest that CP induces respondents to consider more of the profile-related information presented to them compared with CBC

Fast Polyhedral Adaptive Conjoint Estimation

We propose and test new "polyhedral" question design and estimation methods that use recent developments in mathematical programming. The methods are designed to offer accurate estimates after relatively few questions in problems involving many parameters. With polyhedral question design, each respondent's questions are adapted based upon prior answers by that respondent to reduce a feasible set of parameters as rapidly as possible. Polyhedral estimation provides estimates based on a centrality criterion (the "analytic center" of the feasible parameter set). The methods require computer support but can operate in both Internet and other computer-aided environments with no noticeable delay between questions. We evaluate the proposed methods using two approaches. First, we use Monte Carlo simulations to compare the methods against established benchmarks in a variety of domains. In the simulations we compare polyhedral question design to three benchmarks: random selection, efficient Fixed designs, and Adaptive Conjoint Analysis (ACA). We compare polyhedral estimation to Hierarchical Bayes estimation for each question design method. The simulations evaluate the methods across different levels of respondent heterogeneity, response accuracy, and numbers of questions. For low numbers of questions, polyhedral question design does best (or is tied for best) for all domains. For high numbers of questions, efficient Fixed designs do better in some domains. The best estimation method depends on respondent heterogeneity and response accuracy. Polyhedral (analytic center) estimation shows particular promise for high heterogeneity and/or for low response errors. The second evaluation employs a large-scale field test. The field test involved 330 respondents, who were randomly assigned to a question-design method and asked to complete a web-based conjoint exercise. Following the conjoint exercise, respondents were given $100 and allowed to make a purchase from a Pareto choice set of five new-to-the-market laptop computer bags. The respondents received their chosen bag together with the difference in cash between the price of their chosen bag and the$100. We compare the question-design and estimation methods on both internal validity (holdout tasks) and external validity (actual choice of a laptop bag). The field test findings are consistent with the simulation results and offer strong support for the polyhedral question design method. The preferred estimation method varied based on the question design method, although Hierarchical Bayes estimation consistently per-formed well in this domain. The findings reveal a remarkable level of consistency across the validation tasks. They suggest that the proposed methods are sufficiently promising to justify further development. At the time of the test, the bags were prototypes. Based, in part, on the results of this study the bags were launched successfully and are now commercially available. Sales of the features of the laptop bags were consistent with conjoint-analysis predictions

The RNA Binding Protein Quaking Regulates Formation of circRNAs

SummaryCircular RNAs (circRNAs), formed by non-sequential back-splicing of pre-mRNA transcripts, are a widespread form of non-coding RNA in animal cells. However, it is unclear whether the majority of circRNAs represent splicing by-products without function or are produced in a regulated manner to carry out specific cellular functions. We show that hundreds of circRNAs are regulated during human epithelial-mesenchymal transition (EMT) and find that the production of over one-third of abundant circRNAs is dynamically regulated by the alternative splicing factor, Quaking (QKI), which itself is regulated during EMT. Furthermore, by modulating QKI levels, we show the effect on circRNA abundance is dependent on intronic QKI binding motifs. Critically, the addition of QKI motifs is sufficient to induce de novo circRNA formation from transcripts that are normally linearly spliced. These findings demonstrate circRNAs are both purposefully synthesized and regulated by cell-type specific mechanisms, suggesting they play specific biological roles in EMT

Dichotomy in the NRT Gene Families of Dicots and Grass Species

A large proportion of the nitrate (NO3−) acquired by plants from soil is actively transported via members of the NRT families of NO3− transporters. In Arabidopsis, the NRT1 family has eight functionally characterised members and predominantly comprises low-affinity transporters; the NRT2 family contains seven members which appear to be high-affinity transporters; and there are two NRT3 (NAR2) family members which are known to participate in high-affinity transport. A modified reciprocal best hit (RBH) approach was used to identify putative orthologues of the Arabidopsis NRT genes in the four fully sequenced grass genomes (maize, rice, sorghum, Brachypodium). We also included the poplar genome in our analysis to establish whether differences between Arabidopsis and the grasses may be generally applicable to monocots and dicots. Our analysis reveals fundamental differences between Arabidopsis and the grass species in the gene number and family structure of all three families of NRT transporters. All grass species possessed additional NRT1.1 orthologues and appear to lack NRT1.6/NRT1.7 orthologues. There is significant separation in the NRT2 phylogenetic tree between NRT2 genes from dicots and grass species. This indicates that determination of function of NRT2 genes in grass species will not be possible in cereals based simply on sequence homology to functionally characterised Arabidopsis NRT2 genes and that proper functional analysis will be required. Arabidopsis has a unique NRT3.2 gene which may be a fusion of the NRT3.1 and NRT3.2 genes present in all other species examined here. This work provides a framework for future analysis of NO3− transporters and NO3− transport in grass crop species

PAM variants in patients with thyrotrophinomas, cyclical Cushing’s disease and prolactinomas

IntroductionGermline loss-of-function variants in PAM, encoding peptidylglycine α-amidating monooxygenase (PAM), were recently discovered to be enriched in conditions of pathological pituitary hypersecretion, specifically: somatotrophinoma, corticotrophinoma, and prolactinoma. PAM is the sole enzyme responsible for C-terminal amidation of peptides, and plays a role in the biosynthesis and regulation of multiple hormones, including proopiomelanocortin (POMC).MethodsWe performed exome sequencing of germline and tumour DNA from 29 individuals with functioning pituitary adenomas (12 prolactinomas, 10 thyrotrophinomas, 7 cyclical Cushing’s disease). An unfiltered analysis was undertaken of all PAM variants with population prevalence <5%.ResultsWe identified five coding, non-synonymous PAM variants of interest amongst seven individuals (six germline, one somatic). The five variants comprised four missense variants and one truncating variant, all heterozygous. Each variant had some evidence of pathogenicity based on population prevalence, conservation scores, in silico predictions and/or prior functional studies. The yield of predicted deleterious PAM variants was thus 7/29 (24%). The variants predominated in individuals with thyrotrophinomas (4/10, 40%) and cyclical Cushing’s disease (2/7, 29%), compared to prolactinomas (1/12, 8%).ConclusionThis is the second study to demonstrate a high yield of suspected loss-of-function, predominantly germline, PAM variants in individuals with pathological pituitary hypersecretion. We have extended the association with corticotrophinoma to include the specific clinical entity of cyclical Cushing’s disease and demonstrated a novel association between PAM variants and thyrotrophinoma. PAM variants might act as risk alleles for pituitary adenoma formation, with a possible genotype-phenotype relationship between truncating variants and altered temporal secretion of cortisol

—On Managerially Efficient Experimental Designs

In most marketing experiments, managerial decisions are not based directly on the estimates of the parameters but rather on functions of these estimates. For example, many managerial decisions are driven by whether or not a feature is valued more than the price the consumer will be asked to pay. In other cases, some managerial decisions are weighed more heavily than others. The standard measures used to evaluate experimental designs (e.g., -efficiency or -efficiency) do not accommodate these phenomena. We propose alternative “managerial efficiency” criteria (-errors) that are relatively easy to implement. We explore their properties, suggest practical algorithms to decrease errors, and provide illustrative examples. Realistic examples suggest improvements of as much as 30% in managerial efficiency. We close by considering approximations for nonlinear criteria and extensions to choice-based experiments.conjoint analysis, experimental design, product development, efficiency