摘要
具豐富知識與經驗的專家在預測判斷的表現，通常無法達到高準確的預測率，此即所謂的過程與表現的矛盾現象。以往在人為主觀判斷預測的研究中也顯示，專家在預測判斷的表現，不同領域問題的結果不盡相同。這意味著這個現象的存在並不適用於所有專業領域。然而，過去的研究大都侷限於一次或少次數的預測，無法完全呈現資料的意義與代表性，導致分析資料的鑑別度不夠。本研究嘗試藉由台灣上市公司加權股價指數（以下簡稱台股指數）漲跌預測探討此現象。為使實驗結果能準確反應出實際的現象，本研究蒐集連續六十個交易日的預測資料，採網路問卷的實驗方式，方便受測者即時回覆預測值並達成自動資料彙整的目的。實驗數據採集自參與本研究的二十二名受測者。全體受測者依專業能力分為三群，分別為證券專業人士(三位)、學術專業人士(二位)及非專家受測者(十七位)。另以一枚公正硬幣做為隨機預測的資料樣本，藉以形成另一組實驗預測值，與受測者進行方向性預測比較。本研究不僅進行各實驗數據之整體準確度分析，提供專家與非專家於人為判斷準確度與自信度之比較，同時探討於決策過程中，預測準確度的各項影響因子，如校準度、鑑別度、偏誤度、斜率和分散度等指標。由本研究之實驗結果顯示： (1) 雖然有些業餘投資者的個別預測準確度高於證券專家的判斷預測值，但在整體準確度的表現上，證券專家仍優於學界專家、非專家與公正硬幣之預測結果； (2) 專家的判斷預測偏誤值低於非專家的預測偏誤值，這顯示投資經驗對預測準確度產生正面的影響效果；(3) 無經驗的受測群體較其他受測群體在預測表現上，顯現出過度自信的現象；(4)證券專家的預測準確度高於其他受測群體，惟其決策判斷過程中對於樣本基礎率預測的鑑別力指標卻低於其他受測群體。

ABSTRACT
The process-performance paradox describes that highly knowledgeable people often fail to achieve highly accurate judgment. Much research work related to human judgmental forecasts had been done for the test of this paradox, and showed various results in different domains. However, most of the experimental forecasts were limited to perform a very short period with one-time or few time forecasts. The one-time forecasting result could lose its meaning or representativeness if the forecaster is purely lucky to hit the answer, causing a nil-discrimination in data analysis. This study conducted an empirical study in the case of Taiwan Stock Exchange Capitalization Weight Stock Index (TAIEX) directional probabilistic forecasts. To make the experimental results become more accurate so as to reflect practical phenomena, the experiment of this study was planned to collect a period of forecasting data for consecutive 60 business days. A web-based questionnaire was designed to improve the convenience for participants in providing their responses and achieve data gathering automatically. In this experiment, twenty-two voluntary forecasters are divided into three groups (3 security experts, 2 academic experts, and 17 non-professionals) together with a fair coin to make one-day-ahead prediction. The fair coin was used as a random tool to make probabilistic judgment for comparison purpose. Not only a comparison of accuracy in human judgment between professionals and non-professionals was provided, factors affecting the decision process, such as calibration, discrimination, bias, slope, and scat indicators to TAIEX forecast were also considered. The experimental results indicated that (1) on average, professionals’ calibration accuracy is superior to both academic professionals and non-professionals, though the predictive figures of some amateurs outperform professionals; (2) the bias of human judgment in the professionals is less than non-professionals, showing that investment experience provides a positive impact on prediction accuracy; (3) among the three groups, there is a tendency of over-confidence existing in the group of naïves; (4) security professionals have higher overall accuracy and well-calibration in TAIEX forecasts, but there is nil-discrimination regarding sample base rate prediction under the decision process.

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