A run or a streak is a series of the same outcome in a random sample. For example 3 heads in a row in a series of 10 coin flips, or 1000 votes in a row for a single candidate.
Calculating the exact answer requires going over the canonical ensemble and is not practical for large samples, but a proof is done here. However there is a good approximation, as follows:
N is the number of trials, K is the minimum streak size, p is the probability of a single event, and q is the complement, 1-p.
Assume that N is pretty big compared to K. A string of heads (that can be zero heads long) starts with a tails, and there should be about Nq of those. The probability of a particular string of heads being at least K long is p^K so you can expect that there should be around E=Nqp^K strings of heads at least K long. When E≥1, that means that it’s pretty likely that there’s at least one run of K heads. When E<1, E=Nqp^K is approximately equal to the chance of a run of at least K showing up.
Lets put some numbers to this and see what happens
For N=1000, p=q=.5, and K =10
1000*.5*.5^10 = 0.488 or about a 50% chance of getting a string of 10 heads in 1000 coin flips
For N=10,000, p=q=.5, and K =100
10,000*.5*.5^100 = 3.94*10^-27
Already we can see that long streaks are very uncommon . You would be just as likely to win the Powerball lottery three draws in a row ((10^-9)^3 or 10^-27).
Some time tonight, we will be asked to believe that a streak of 1000 showed up in 100,000 votes
For N=100,000, p=q=.5, and K =1000
100000*.5*.5^1000 = 4.67*10^-297
and for those of you that say votes are not coin flips
For N=100,000, p=.6, q=.4, and K =1000 giving a 10% advantage to Mcluffie, completely unrealistic.
100000*.4*.6^1000 = 5.67*10^-218
This is at the same level as winning every single Powerball lottery for an entire year. It is an event that will never occur in a universe of universes. So either they either are ruling by divine right, or they are stealing our government.
When I saw "Runs and Streaks" in the title, I thought the post would be about Biden.
I agree with your analysis, however you can't go by the overall election numbers for the state unless the pool of votes being counted randomly comes from there.
You need to look at the precinct level, it is known that some cities/areas can be 98% D, and when those were added to the total.
With areas that are high % D that are densely populated, ballot harvesting becomes extremely effective. Even more so if the population has a lot of people that need to be "assisted" with their voting, or may just give up a blank ballot to a harvester.
So what's the deal here? Even the BBC is calling it for Youngkin now, is it actually mathematically impossible for McAuliffe to win, or is it merely the in-person votes that Youngkin has won, postal votes to fortify as necessary?
I wrote this out before any of the media had called it, expecting it to be like 2020. (for that matter McAuliffe hasn't conceded yet. )
Keep in mind this is just the math behind streaks, if no one saw any streaks, then it is not useful. I also cannot edit it, but that is not very important.