Answer
$µ_{NT}=µ_{SP}\neµ_{SD}$
Spring Disk.
Work Step by Step
The interval for $µ_{SD}-µ_{SP}$ is entirely positive, that is, it does not contain the zero.
The interval for $µ_{NT}-µ_{SP}$ contains the zero.
The interval for $µ_{NT}-µ_{SD}$ is entirely negative, that is, it does not contain the zero.