The model assumes the availability of all the relevant information for the decision making process. Perfect information for decision making cannot exist and there will always be some information missing in the real life decision making process. This makes the reliability of the decisions made based on this model questionable.
The rational decision making model assumes that it is possible to consider all the possible alternative outcomes available for the making of a decision. The process of identifying all the possible choices that can be made in a decision is time wasting and therefore makes the model unreliable.
An assumption is made by the model that there is only one possible best outcome. In case the outcomes have very small differences, choice of the best outcome may be a very difficult task. This process of choosing the best option may delay the decision and impact negatively on the reliability of the ultimate decision that is made based on the model.
The future consequences of each decision alternative are assumed to be known beforehand before a choice is made. This makes the model an unreliable tool in the decision making process because of it is impossible to predict the future accurately. Decisions made by the use of the model based on some assumed future conditions may turn out to be wrong because of an unanticipated deviation of the conditions from those predicted.
The rational decision making model depends on the cognitive abilities of the decision maker. Abilities like the decision maker’s memory or imagination will influence the quality of decision made. Since such abilities are of different levels among different individuals, decisions made by the use of the rational decision making model by different individuals based on the same set of facts will be different depending on every particular individual’s reasoning ability. This illustrates how the model can de an unreliable tool of decision making.
The model assumes that human emotions play no role in the choice of the decision alternative. This is almost impossible because human emotions cannot be written off many decision making processes. A decision maker cannot thus claim to be absolutely dispassionate in the making of a decision. This assumption of the model that human emotions do not play a role in decision making makes it unreliable.
In conclusion, it can be argued that the rational decision making model claim that decisions can be made by following a logical, linear progression in our mind is untrue. The assumptions that the model makes make its suggested procedure decision making full of weaknesses and as a result make it unreliable.