Before revision: Normal shmoo plot Abnormal shmoo plot If a sufficiently-wide range of variables were to be tested, a normal shmoo plot would show an operating envelope of some shape not unlike Al Capp's Shmoo, but in practice, this might damage the device under test, and finer-grained views are of much more interest, particularly focusing on published component margins (e.g., - 5% Vcc).
After revision: Normal shmoo plot Abnormal shmoo plot If a sufficiently-wide ranges of the two independent vriables were to be tested, a normal shmoo plot would show an operating envelope of some shape not unlike Al Capp's Shmoo, but in practice, this might damage the device under test, and finer-grained views are of much more interest, particularly focusing on published component margins (e.g., - 5% Vcc).