Precision, Recall and Threshold

Course Q&A Machine Learning Specialization Advanced Learning Algorithms
1

Can someone explain to me more clearly what Propf. Ng means by his explanation of the effect of raising the threshold from 0.5 to 0.7 on the Recall metric?

“…but it also results in lower recall because we’re now predicting one less often and so of the total number of patients with the disease, we’re going to correctly diagnose fewer of them.”

He says “…one less often…”, one what?

I think I get it now but he could have explained it much, much better than this!

2

Hi Stephen,

I think he means “…we’re now predicting 1 less often…” or “…we’re now predicting the positive class less often…”