Q1. What is accuracy?
Accuracy is the number of correct predictions out of all predictions made.

Accuracy=True Positives+True NegativesTotal Number of Predictions

Q2. Why is accuracy not a good measure for classification problems?
Accuracy is not a good measure for classification problems because it gives equal importance to both false positives and false negatives. However, this may not be the case in most business problems. For example, in the case of cancer prediction, declaring cancer as benign is more serious than wrongly informing the patient that he is suffering from cancer. Accuracy gives equal importance to both cases and cannot differentiate between them.