Plurality Voting:

In the case of plurality rule weightage is assigned in the ratio n: 1 for the best preference and the least preference among n, alternative outcomes.  In between (n-1), (n-2), (n-3),......... weightage will be fixed for the rest outcomes in descending order on the basis of order of preference accordingly. 

Suppose there are three individuals X, Y and Z and there are five alternative outcomes

such as a, b, c, d and e.

 
  X:  a > b > c > d > e
  Y:  a > b > c > d > e
  Z:   c >d > e > a > b

Applying the majority rule the group choice will be a > b > c > d > e and 'Z' will be the minority.
 
In terms of plurality rule weight age will be assigned as follows 

  a > c > b > d > e
 
In comparison to majority rule outcome 'c' the best preference of 'Z' (the minority) is getting importance in the plurality rule as it is placed on the second place in the group preference.  It is on the third place in the group preference under the majority rule. The best preference of the majority is 'a' whereas the best preference of the minority is 'c'. In the case of comparison between 'a' and 'c', 'b' is considered as irrelevant.
 
Let us omit 'b'.
 
This results as follows in terms of the preference pattern.
  
  X:  a >c >d >e
  Y:  a >c >d >e
  Z:  c >d >e >a 
 
The group preference will be a >c > d > e according to the majority rule.  According to the plurality rule from Table 6.2 it is found that group preference will be
 
  c > a > d >e 

Comparing Majority and the Plurality rule in this case it can be stated that the majority rule is independent of the irrelevant alternative (i.e. 'b') whereas plurality rule is not. 

Referring to Arrow's  "Rational Collective  Choice" it is seen that plurality rule violates the axiom of  'independence of irrelevant alternative'. Hence plurality rule cannot be considered for the derivation of group choice.   However the supporters of plurality rule do not agree to it.  In  accordance with, Musgrave the concept of 'irrelevant alternative' is valid only in the competition for scoring in the examination or athletic contest so that when we consider the first and second in the   merit list or as the prizewinner, the third position becomes irrelevant. This is not true in the case of revealing preference for different alternative outcomes as the set of alternatives comprising all outcomes set up the mind  of an individual for expressing his preference.