Fig. 1 - Call outcome percentages and ring times
These are outcomes where there is no response to the ringing tone made on a telephone number that has been called. Sometimes called Ring No Answer (RNA). You will need to decide how long the ring time should be (Fig. 1).
Be careful about setting it too high, for example more than 20 seconds. Chances are that if you don't get an answer by then, you are not going to. If you are not sure about this, do some experiments with the average times and variances for the six types of call outcomes.
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