Browsing by Subject "Judgmental forecasting"
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Item Open Access Antecedents and effects of trust in forecasting advice(Elsevier, 2013) Goodwin, P.; Gönül, M. S.; Önkal D.Forecasting support systems (FSSs) have little value if users distrust the information and advice that they offer. Two experiments were used to investigate: (i) factors that influence the levels of users’ stated trust in advice provided by an FSS, when this advice is provided in the form of interval forecasts, (ii) the extent to which stated trust is associated with users’ modifications of the provided forecasts, and (iii) the consequences of these modifications for the calibration of the interval forecasts. Stated trust was influenced by the levels of noise in time series and whether a trend was present but was unaffected by the presence or absence of point forecasts. It was also higher when the intervals were framed as ‘best-case/worst-case’ forecasts and when the FSS provided explanations. Absence of trust was associated with a tendency to narrow the provided prediction intervals, which reduced their calibration.Item Open Access The effects of feedback and training on the performance of probability forecasters(Elsevier, 1992) Benson, P. G.; Önkal D.An experiment examined the effects of outcome feedback and three types of performance feedback-calibration feedback, resolution feedback, and covariance feedback - on various aspects of the performance of probability forecasters. Subjects made 55 forecasts in each of four sessions, receiving feedback prior to making their forecasts in each of the last three sessions. The provision of calibration feedback was effective in improving both the calibration and overforecasting of probability forecasters, but the improvement was not gradual; it occurred in one step, between the second and third sessions. Simple outcome feedback had very little effect on forecasting performance. Neither resolution nor covariance feedback affected forecasters' performances much differently than outcome feedback. However, unlike outcome feedback, the provision of performance feedback caused subjects to manage their use of the probability scale. Subjects switched from two-digit probabilities to one-digit probabilities, and those receiving calibration and resolution feedback also reduced the number of different probabilities they used. © 1992.Item Open Access The effects of feedback on judgmental interval predictions(Elsevier, 2004) Bolger, F.; Önkal-Atay, D.The majority of studies of probability judgment have found that judgments tend to be overconfident and that the degree of overconfidence is greater the more difficult the task. Further, these effects have been resistant to attempts to ‘debias’ via feedback. We propose that under favourable conditions, provision of appropriate feedback should lead to significant improvements in calibration, and the current study aims to demonstrate this effect. To this end, participants first specified ranges within which the true values of time series would fall with a given probability. After receiving feedback, forecasters constructed intervals for new series, changing their probability values if desired. The series varied systematically in terms of their characteristics including amount of noise, presentation scale, and existence of trend. Results show that forecasts were initially overconfident but improved significantly after feedback. Further, this improvement was not simply due to ‘hedging’, i.e. shifting to very high probability estimates and extremely wide intervals; rather, it seems that calibration improvement was chiefly obtained by forecasters learning to evaluate the extent of the noise in the series. D 2003 International Institute of Forecasters. Published by Elsevier B.V. All rights reserved.Item Open Access Effects of feedback on probabilistic forecasts of stock prices(1995) Önkal D.; Muradoğlu, G.This paper reports the results of an experiment in stock-price forecasting that investigated the effects of feedback on various dimensions of probability forecasting accuracy. Three types of feedback were used: (1) simple outcome feedback, (2) outcome feedback presented in the task format, and (3) performance feedback in the form of an overall accuracy score in addition to detailed calibration information. While calibration improved for all the feedback groups, forecasters' skill was found to improve only for the task-formated outcome feedback and performance feedback groups (but not for the simple outcome feedback group). Finally, the forecasters in the performance feedback group also improved their mean slope and mean probability scores, an effect not observed in the other feedback groups. It is suggested that, in a dynamic environment like the stock market, probability forecasting offers distinct advantages by providing an important channel of communication between the forecasters and the users of financial information.Item Open Access Effects of ignorance and information on judgments and decisions(Society for Judgment and Decision Making, 2011) Ayton, P.; Önkal D.; McReynolds, L.We compared Turkish and English students’ soccer forecasting for English soccer matches. Although the Turkish students knew very little about English soccer, they selected teams on the basis of familiarity with the team (or its identified city); their prediction success was surprisingly similar to knowledgeable English students—consistent with Goldstein and Gigerenzer’s (1999; 2002) characterization of the recognition heuristic. The Turkish students made forecasts for some of the matches with additional information—the half-time scores. In this and a further study, where British students predicting matches for foreign teams could choose whether or not to use half-time information, we found that predictions that could be made by recognition alone were influenced by the half-time information. We consider the implications of these findings in the context of Goldstein and Gigerenzer’s (2002, p. 82) suggestion that “. . . no other information can reverse the choice determined by recognition” and a recent more qualified statement (Gigerenzer & Goldstein, 2011) indicating that two processes, recognition and evaluation guide the adaptive selection of the recognition heuristic.Item Open Access Effects of task format on probabilistic forecasting of stock prices(Elsevier, 1996) Önkal D.; Muradoğlu, G.This study aims to explore the differences in various dimensions of forecasting accuracy that may result from the task format used to elicit the probabilistic forecasts. In particular, we examine the effects of using multiple-interval and dichotomous formats on the performance of portfolio managers' probabilistic forecasts of stock prices. Probabilistic forecasts of these experts are compared with those provided by semi-experts comprised of other banking professionals trained in portfolio management, as well as with forecasts provided by a novice group. The results suggest that the task format used to elicit the probabilistic forecasts has a differential impact on the performance of experts, semi-experts, and novices. The implications of these findings for financial forecasting are discussed and directions for future research are given.Item Open Access Effects of trend strength and direction on performance and consistency in judgmental exchange rate forecasting(Elsevier, 2013) Thomson, M. E.; Pollock, A. C.; Gönül, M. S.; Önkal D.Using real financial data, this study examines the influence of trend direction and strength on judgmental exchange rate forecasting performance and consistency. Participants generated forecasts for each of 20 series. Half of the participants also answered two additional questions regarding their perceptions about the strength and direction of the trend present in each of the series under consideration. The performance on ascending trends was found to be superior to that on descending trends, and the performance on intermediate trends was found to be superior to that on strong trends. Furthermore, the group whose attention was drawn to the direction and strength of each trend via the additional questions performed better on some aspects of the task than did their “no-additional questions” counterparts. Consistency was generally poor, with ascending trends being perceived as being stronger than descending trends. The results are discussed in terms of their implications for the use and design of forecasting support systems.Item Open Access Expertise, credibility of system forecasts and integration methods in judgmental demand forecasting(Elsevier B.V., 2017) Alvarado-Valencia, J.; Barrero, L. H.; Önkal D.; Dennerlein, J. T.Expert knowledge elicitation lies at the core of judgmental forecasting—a domain that relies fully on the power of such knowledge and its integration into forecasting. Using experts in a demand forecasting framework, this work aims to compare the accuracy improvements and forecasting performances of three judgmental integration methods. To do this, a field study was conducted with 31 experts from four companies. The methods compared were the judgmental adjustment, the 50–50 combination, and the divide-and-conquer. Forecaster expertise, the credibility of system forecasts and the need to rectify system forecasts were also assessed, and mechanisms for performing this assessment were considered. When (a) a forecaster's relative expertise was high, (b) the relative credibility of the system forecasts was low, and (c) the system forecasts had a strong need of correction, judgmental adjustment improved the accuracy relative to both the other integration methods and the system forecasts. Experts with higher levels of expertise showed higher adjustment frequencies. Our results suggest that judgmental adjustment promises to be valuable in the long term if adequate conditions of forecaster expertise and the credibility of system forecasts are met.Item Open Access Judgmental adjustments of previously adjusted forecasts(Wiley-Blackwell Publishing, 2008) Önkal D.; Gönül, M. S.; Lawrence, M.Forecasts are important components of information systems. They provide a means for knowledge sharing and thus have significant decision-making impact. In many organizations, it is quite common for forecast users to receive predictions that have previously been adjusted by providers or other users of forecasts. Current work investigates some of the factors that may influence the size and propensity of further adjustments on already-adjusted forecasts. Two studies are reported that focus on the potential effects of adjustment framing (Study 1) and the availability of explanations and/or original forecasts alongside the adjusted forecasts (Study 2). Study 1 provides evidence that the interval forecasts that are labeled as "adjusted" are modified less than the so-called "original/unadjusted" predictions. Study 2 suggests that the provision of original forecasts and the presence of explanations accompanying the adjusted forecasts serve as significant factors shaping the size and propensity of further modifications. Findings of both studies highlight the importance of forecasting format and user perceptions with critical organizational repercussions.Item Open Access Judgmental forecasting(Wiley, 2004) Önkal-Atay, Dilek; Thomson, M. E.; Pollock, A. C.; Clements , M. P.; Hendry, D. F.