Editing Exponential backoff (section)

==Expected backoff==
Given a [[Discrete uniform distribution|uniform distribution]] of backoff times, the [[expected value|expected]] backoff time is the mean of the possibilities. After ''c'' collisions in a binary exponential backoff algorithm, the delay is randomly chosen from {{math|[0, 1, ..., ''N'']}} slots, where {{math|1=''N'' = 2<sup>''c''</sup> − 1}}, and the expected backoff time (in slots) is
:<math>\operatorname{E}(c) = \frac{1}{N+1}\sum_{i=0}^{N} i = \frac{1}{N+1}\frac{N(N+1)}{2} = \frac{N}{2}.</math>

For example, the expected backoff time for the third ({{math|1=''c'' = 3}}) collision, one could first calculate the maximum backoff time, ''N'':
:<math>N = 2^c - 1</math>
:<math>N = 2^3 - 1 = 8 - 1</math>
:<math>N = 7 ,</math>
and then calculate the mean of the backoff time possibilities:
:<math>\operatorname{E}(c) = \frac{1}{N+1}\sum_{i=0}^{N} i = \frac{1}{N+1}\frac{N(N+1)}{2} = \frac{N}{2} = \frac{2^c-1}{2}</math>.
which is, for the example, {{math|1= ''E''(3) = 3.5}} slots.