Thinking about it, if the clock runs backwards at the same rate, so -1 hour per hour, the rate of randomly being right is 2x the stand-still rate. This is also a linear function, at -1 its 4x per day, -0.5 is 3/d, 0 is 2, 0.5 is 1. When it runs true it is however very different, as it is either always exactly right (no offset) or never (with offset).
Thinking about it, if the clock runs backwards at the same rate, so -1 hour per hour, the rate of randomly being right is 2x the stand-still rate. This is also a linear function, at -1 its 4x per day, -0.5 is 3/d, 0 is 2, 0.5 is 1. When it runs true it is however very different, as it is either always exactly right (no offset) or never (with offset).
A broken clock running 6x its speed will also be correct much more often than a stopped clock.