# Thread: Calculating a probability from a pdf.

1. ## Calculating a probability from a pdf.

Need help with a question guys, any help will be most appreciated.

The age of a machine, x, in years, is related to the probability of breakdown, y, by the formula:

x = 3 + ln(y/1-y)

Determine the probability of breakdown for 1, 3 and 10 years.

It has got me a bit stumped guys so any help would be most appreciated.

Thanks

2. The age of a machine, x, in years, is related to the probability of breakdown, y, by the formula:

x = 3 + ln(y/1-y)

Determine the probability of breakdown for 1, 3 and 10 years.
For example, $10=3+\ln(y/(1-y))$; we need to find y. Then $\ln(y/(1-y))=7$. Raise $e$ to both sides keeping in mind that $e^{\ln a}=a$ for all $a>0$. This will give you a linear equation on y. Formally, after finding y, you must check that $y/(1-y) > 0$ to make sure that $\ln(y/(1-y))$ exists because when one raises e to both sides of an equation, one can acquire spurious roots.