If the dataset is balanced, we can use accuracy which is TP + TN /(TP+FP+TN+FN)
If the dataset is unbalanced, we can use precision, recall and F1 score
Precision=TP/TP+FP
Recall=TP/TP+FN
F1score= 2*precision*recall/(precision+recall)
Where TP=True Positive
FP=False Positive
TN=True Negative
FN=False Negative
Answer ( 1 )
If the dataset is balanced, we can use accuracy which is TP + TN /(TP+FP+TN+FN)
If the dataset is unbalanced, we can use precision, recall and F1 score
Precision=TP/TP+FP
Recall=TP/TP+FN
F1score= 2*precision*recall/(precision+recall)
Where TP=True Positive
FP=False Positive
TN=True Negative
FN=False Negative