德尔非法是在20世纪40年代由O．赫尔姆和N．达尔克首创，经过T．J．戈尔登和兰德公司进一步发展而成的。德尔菲这一名称起源于古希腊有关太阳神阿波罗的神话。传说中阿波罗具有预见未来的能力。因此，这种预测方法被命名为德尔菲法。1946年，兰德公司首次用这种方法用来进行预测，后来该方法被迅速广泛采用。
德尔菲法依据系统的程序，采用匿名发表意见的方式，即专家之间不得互相讨论，不发生横向联系，只能与调查人员发生关系，通过多轮次调查专家对问卷所提问题的看法，经过反复征询、归纳、修改，最后汇总成专家基本一致的看法，作为预测的结果。这种方法具有广泛的代表性，较为可靠。
德尔非法的具体实施步骤如下
（1）组成专家小组。按照课题所需要的知识范围，确定专家。专家人数的多少，可根据预测课题的大小和涉及面的宽窄而定，一般不超过20人。
（2）向所有专家提出所要预测的问题及有关要求，并附上有关这个问题的所有背景材料，同时请专家提出还需要什么材料。然后，由专家做书面答复。
（3）各个专家根据他们所收到的材料，提出自己的预测意见，并说明自己是怎样利用这些材料并提出预测值的。
（4）将各位专家第一次判断意见汇总，列成图表，进行对比，再分发给各位专家，让专家比较自己同他人的不同意见，修改自己的意见和判断。也可以把各位专家的意见加以整理，或请身份更高的其他专家加以评论，然后把这些意见再分送给各位专家，以便他们参考后修改自己的意见。
（5）将所有专家的修改意见收集起来，汇总，再次分发给各位专家，以便做第二次修改。逐轮收集意见并为专家反馈信息是德尔菲法的主要环节。收集意见和信息反馈一般要经过三、四轮。在向专家进行反馈的时候，只给出各种意见，但并不说明发表各种意见的专家的具体姓名。这一过程重复进行，直到每一个专家不再改变自己的意见为止。
（6）对专家的意见进行综合处理。
如某书刊经销商采用德尔非法对某一专著销售量进行预测。该经销商首先选择若干书店经理、书评家、读者、编审、销售代表和海外公司经理组成专家小组。将该专著和一些相应的背景材料发给各位专家，要求大家给出该专著最低销售量、最可能销售量和最高销售量三个数字，同时说明自己作出判断的主要理由。将专家们的意见收集起来，归纳整理后返回给各位专家，然后要求专家们参考他人的意见对自己的预测重新考虑。专家们完成第一次预测并得到第一次预测的汇总结果以后，除书店经理B外，其他专家在第二次预测中都做了不同程度的修正。重复进行，在第三次预测中，大多数专家又一次修改了自己的看法。第四次预测时，所有专家都不再修改自己的意见。因此，专家意见收集过程在第四次以后停止。最终预测结果为最低销售量26万册，最高销售量6O万册，最可能销售量46万册。
參考答案:Deuel illegal is originates in the 20th century 40's by O. Helm and N. Dalke, further develops after T.J. Golden and the Rand Corporation becomes. Deuel Philippines this beginning of name in ancient Greece related sun god Apollo's myth. In the fable Apollo will have the foresight future ability. Therefore, this forecast method is named as the Deuel Philippines method. In 1946, the Rand Corporation used this method to use for the first time to carry on the forecast, afterwards this method by rapid widespread use.
The Deuel Philippines method basis system procedure, uses anonymous publishes the opinion way, namely between the expert does not have to discuss mutually, does not have the crosswise relation, only can have the relations with the investigator, time investigates the expert through the multiwheel to ask the question to the questionnaire the view, passes through seeks information, the induction, the revision repeatedly, finally compiles the expert basic consistent view, takes the forecast the result. This method has the widespread representation, more reliable.
Deuel's illegal concrete implementation step as follows
(1) forms the technical panel. Knowledge scope needs which according to the topic, definite expert. Expert population how many, may decides according to the forecast topic size and the affected area width, does not surpass 20 people generally.
(2) to all experts proposed must forecast the question and the related request, and enclosed concern this question all background material, simultaneously asks the expert to propose also needs any material. Then, gives the written reply by the expert.
(3) each expert according to the material which they receive, proposed own forecast opinion, and showed how oneself is uses these materials and proposes the forecast value.
(4) compiles fellow experts first judgment opinion, the row becomes the graph, carries on the contrast, again distributes for fellow experts, lets the expert compare oneself with other people different opinion, revises own opinion and the judgment. Also may reorganize fellow expert opinion, or asks status higher other experts to comment, then sends again these opinions for fellow experts, after in order to they refer revise own opinion.
(5) will possess expert's revision opinion to collect, will compile, will distribute once more for fellow experts, in order to make the second revision. Feeds back the information by the turn collection opinion and for the expert is the Deuel Philippines's method key link. The collection opinion and the information feedback must pass through generally three, four turns. In carries on to the expert feeds back, only gives each opinion, but did not explain publishes each opinion expert's specific name. This process repetition carries on, no longer changes own until each expert opinion.
(6) pair of expert opinion carries on synthesis processing.
If some books and periodicals dealer uses Deuel illegally to carry on the forecast to some monograph sales volume. This dealer first chooses certain bookstore managers, the book review, the reader, the editor, the sale represents with overseas company executive forms the technical panel. Issue fellow experts this monograph and some corresponding background material, requests everybody to give this monograph lowest sales volume, the most possible sales volume and the highest sales volume three numerals, simultaneously explained oneself makes the judgment the major reason. Collects the expert opinion, after the induction reorganizes returns for fellow experts, then requests the experts to refer to other people opinion to reconsider to own forecast. The experts complete first time forecast and obtains the first forecast compiles after the result, besides bookstore Manager B, other experts in the second forecast has all made the varying degree revision. The repetition carries on, in the third forecast, the majority experts revised own view once again. When fourth forecast, all experts all no longer revise own opinion. Therefore, the expert advice collection process will stop in fourth later. Finally forecasts the result for the lowest sales volume 260,000 volume, highest sales volume 6O ten thousand volume, most possible sales volume 460,000 volume.
