You can specify two Y columns when some of the degradation measurements are interval censored or left censored. For a given row, the values in the two Y columns determine the type of censoring.
• If the two Y values are equal and neither is missing, then the common measurement is treated as exact.
• If the two Y values are not equal and neither is missing, then the measurement is interval censored and assumed to be between the two values.
• If only the first value is missing, then the measurement is left censored and assumed to be smaller than the second value.
• If only the second value is missing, then the measurement is right censored and assumed to be larger than the first value.
Note: The only way to fit left-censored measurements in the Destructive Degradation platform is through the use of two Y columns.