IFR (increasing failure rate) : survival function/failure function, 1-F(x), is logconcave.
DFR (decreasing failure rate) : survival function/failure function, 1-F(x), is logconvex.
Failure rate/Hazard rate : h(x)=f(x)/(1-F(x))
IFR (increasing failure rate) : survival function/failure function, 1-F(x), is logconcave.
DFR (decreasing failure rate) : survival function/failure function, 1-F(x), is logconvex.
Failure rate/Hazard rate : h(x)=f(x)/(1-F(x))