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.