Originally posted by: user1234
Originally posted by: Steve Guilliot
Realize that 50,000 MTBF means the power supply is 50% likely to die within 5.7 years, not that we are guaranteed a working power supply for 5.7 years.
i.e. A 100,000 MTBF is approx. half as likely to die within x years as 50,000 MTBF.
Statistics 101 - a 100K MTBF PSU is only half as likely to die within x number of years as a 50K unit, if the distribution of failure times is uniform. But usually these things have a bell curve distribution, which means that the 100K unit has much much less than half the propability to die within x years than the 50K unit, if x is less than 100K hours. When x is exactly 100K the probability ratio is about half - that is the 100K unit has 50% chance to die within 100K hours, while the 50K unit has 99% chance to die within 100K hours.
When x is 50K hours - the 50K unit has 50% chance to die, and the 100K unit has about 10% chance to die (remember, bell curve), so you could say that the 50K unit is 5 times more likely to die within 50K hours.
Next time: Statistics 102...