本研究主要在探討分析師在做盈餘預測時，是否會有過度樂觀及過度自信之偏誤，以及分析師盈餘預測過度樂觀與過度自信之強弱關聯，研究結果發現，在沙賓法案通過之前，分析師盈餘預測存在過度樂觀之偏誤，而當分析師接受到較佳的訊息時，所作的盈餘預測過度樂觀程度也較為嚴重，且過度樂觀之偏誤在空頭市場時較多頭市場強烈。此外，亦發現沙賓法案通過之前，分析師盈餘預測會過度重視其本身之私有資訊，且當分析師接受到較佳訊息時，其分析師的資訊權重偏誤行為來自於誘因假說。為符合研究需要，本研究截取出分析師過度著重其私有資訊之偏誤是來自於分析師本身的過度自信之樣本，以進行分析師盈餘預測過度樂觀與過度自信之強弱關聯之研究，結果發現，分析師盈餘預測過度樂觀偏誤較嚴重，其過度自信之偏誤亦較強，而過度自信偏誤較嚴重之樣本，其過度樂觀的程度亦較高。而在盈餘預測共識值準確度與交易量之分析中，研究發現盈餘預測共識值準確度與成交量為正向相關，且資訊透明度較高的公司，盈餘預測共識值準確度對交易量之影響較大。

The purpose of this study comprehend the relationship between overoptimism and overconfidence when analysts forecast earnings, the results found that prior to the Sarbanes-Oxley Act, analysts forecast exist overoptimism, and when analysts receive a better message and recession, the degree of overoptimism is more serious. In addition, also found that prior to the Sarbanes-Oxley, analysts overweight their private information in their earnings forecast, and when analysts receive a better message, the overweight bias comes from incentives hypothesis. To meet the research needs, the study choose data whose overweight bias comes from overconfidence hypothesis, and the result found that analyst earnings forecasts overoptimism is more serious, the bias of overconfidence is stronger, and the overconfidence more is serious, the degree of overoptimism is stronger. The study also found that the accuracy of earnings forecast is positive correlation with the trading volume, and higher corporation information transparency, the accuracy of earnings forecast of the impact on trading volume larger.

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