Misclassification Rate measures the overall proportion of observations that were wrongly classified or mis-classified.
Misclassification Rate = 1 – Accuracy
where Accuracy = (True Positives + True Negatives) / Total Observations
Using an example:
Accuracy is = (100 + 150) /360 = .694
Misclassification Rate = 1 – 0.694 = 0.306