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If we use the cherry shaft body manufacturers said a shaft body key life is greater than 50 million times, so we assume that, at first to get the shaft body is always perfect and could not be a problem (after all, start with quality inspection), so this time the probability of failure of the shaft body is 0, then the shaft body normal use probability is 1. Then we do the most conservative estimate, is the target of according to the factory (specific indicators is not clear, from the reasonable hypothesis).
If press after 50 million times, the probability of the axis of the body is still the perfect job is greater than 3 sigma principle can think shaft body life 50 million, that is to say 50 million times, the probability of shaft body work is 99.7%, that is to say, the shaft body problem rate is 0.3% after 50 million or 0.003, then we continue to do a simple hypothesis, is along with the increase of the press the number axis body rate and the pressure is directly proportional to the number of bearing on the matter, That is to say, as the number of presses increases slowly, the problem rate becomes higher and higher. (after all, cherry guarantees that 50 million presses on the shaft within two years are within the scope of warranty and product specifications, which is a reasonable assumption.)
So we can get the average press all the buttons after N times that keyboard 104 shaft body is not a problem of probability is: P = (1-0.003 / (5 * 10 ^ 7) * N] ^ 104
At this point, we can draw a graph showing the normal utilization rate of the keyboard after N presses in an average of two years and the probability that the keyboard has an axial body regardless of whether Pw = 1-p
Where the X-axis is the average number of keys N and the Y-axis is Pw, which is the probability that the keyboard axis will not work. The red line is the relation between the probability and the number of keystrokes on the keyboard body regardless of the probability. The blue line represents 0.003, which is the 3sigma principle of 0.3%. And this is the ideal assumption, which is to say that the expected number of keyboard problems is the same as the expected number of problems for a single axis.
And it's in the ideal environment. If I according to the assumption day next door type 3 k (this is not much), then use the pinyin is roughly 1 w presses, because is the punctuation and Spaces, in fact, 50 million presses is 5 k days almost 15 years, that is to say, according to the theory of probability, the keyboard is very likely in 15 years, won't appear the shaft body damage. But don't forget. Cherry's technical parameters also have warranty period, only two years, that is, more than two years, the probability of damage should be higher than the rated life. So 15 years is just a theoretical number, and it's definitely going to be less than that.