1. A process theory proposed by Victor Vroom in 1964
Expectancy Theory
A process theory proposed by Victor Vroom in 1964
Expectancy theory is about the mental processes involved in making choices;
Vroom was of the view that employees consciously decide whether to perform or not at the job; the theory suggests that individuals decide to act in a certain way because they are motivated to select a behaviour over other behaviours based on their expectation of the result.
The individual selects their behaviour based on the perception of how well the expected results of a given behaviour are going to match up with the desired results.
The motivational force behind the chosen behaviour is determined by the desirability of the expected outcome/results.
The theory can also be referred to as the valence – instrumentality expectancy theory which stems from Vrooms own analysis made up of three key factors;
The individuals expectancy that the effort will lead to the intended performance
The instrumentality of this performance in achieving a certain result
The desirability of the result (known as valence) to the individual

2. Expectancy Theory explored
Expectancy theory provides a framework for thinking about how people make choices based upon expectations. Focusing on expectations allows the theory to account for differences in choices between people despite the actual amount of effort necessary to achieve rewards and the actual value of rewards.
The formula for expectancy looks like this;
MF = EXPECTANCY X ISTRUMENTALITY X VALENCE
The formula expectancy times instrumentality times valence also agrees with basic intuition regarding motivation. If any of the three values that make up MF is zero, MF also equals zero. This makes intuitive sense: If someone believes his effort will have no chance of resulting in a certain reward, that a certain performance level will not lead to a reward or that a reward will have no value, he will have no motivation to work toward the reward. (source; ehow, strengths and weaknesses of the expectancy theory by Gregory Hamel)

3. Something to consider;
As the theory is primarily based on individual perception regarding effort, performance and the value or desirability of reward it is difficult to quantify so comparisons between different choices or people using the expectancy framework may not be accurate.
When considering the different motivational theories and performance management it’s important to look at the different reward systems as not all reward is related or directly connected to effort and performance, for instance in the public sector it is not unusual for employees to receive annual or incremental pay rises.
In contradiction to this the expectancy theory implies that individuals will only put effort toward something for a reward, this implication also conflicts with altruism, which describes actions done purely to benefit others without regard for personal rewards.