A binomial distribution.
 
P = probability of being absent  
q = probability of not being absent 
r = total number of “successes” ( heads or tails etc.) 
n = number of consoltant workers 
c =   
Tip: You can use the combinations calculator to figure out the value for 
nC
r 
                        P
r = 
nC
r x P
rq
n-r 
                    n = 6, Q = 1 - 0.2 = 0.8 
                    P(r ≥ 3) = 1 - [P(r = 0) + P(r = 1) + P(r = 2)] 
                    P(r = 0) = 6C
0 x (0.2)
0(0.8)
6-0
                    = 0.2621 
                    P(r = 1) = 6C
1 x (0.2)¹ (0.8)
6-1 
                    = 
6C₁ x (0.2)¹(0.8)
5 = 0.3932 
                    P(r=2)= 
6C
2x (0.2)
2(0.8)
4 = 0.2458 
                      
                    Thus, P(r ≥ 3) = 1 - (0.2621 + 0.3932 + 0.2458) 
                    =1 - 0.9011 
                    = 0.0989 
                    Therefore, there is a chance or probability of 0.989 that more than two consultants will be absent from work on a given day. 
                   
 A Poisson distribution.
 
                    
                    
                     
                    r is a random variable following a Poisson distribution
n is the number of times an event occurs
P(X = n) is the probability that an event will occur k times
e is Euler’s constant (approximately 2.718)
λ (lambda) is the average number of times an event occurs
! is the factorial function 
                    P(r ≥3) = 1 - [P(r = 0) + P(r = 1) + P(r = 2)] 
                 
                    e = 2.7183 
                    λ = 20% x 6 = 1.2 
                    
                    
                      = 0.3012 
                    
                    
                      = 0.3614 
                    
                    
                      = 0.2169 
                    ∴P(r ≥) = 1 - (0.3013 + 0.3614 + 0.2169) 
                    =1 - 0.8795 = 0.1205 
                   Therefore, there is a chance or probability of 0.1205 that more than two consultants will be absent from mark on a given day.