[P] PCA and the use of Unsupervised Machine Learning for Fraud Detection? Is there any way to evaluate an unsupervised model?

I hope my questions don't sound too stupid, but I'm new to data science and currently trying to delve deeper into fraud analytics and I'm very very confused.

I'm doing this project where I was given a raw dataset of online transactions and told to define normal and anomalous behavior in my own terms.

As for what I read, common evaluation metrics used for fraud detection include precision, recall, F1-score, ROC curve, or confusion matrix. But I can't get the …

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