I'm completing a DataCamp course where we are introduced to the log loss formula for binary classification:
Two scenarios are given to show how the formula is used. One with p=0.1 and one with p=0.5. The answers the instructor displayed were 2.3 and .69, respectively. However, using a calculator, the answers for log(0.1) and log(0.5) are -1 and -0.30, respectively. I later tried using natural log instead and got the same answers as the instructor, except negative. Specifically, the calculator returned -2.3 for ln(0.1) and -0.69 for ln(0.5).
Is it common in math for log to implied to be "ln" or "log e" without stating it explicitly in the formula? Also, is there something about the log loss binary classification formula that suggest that the absolute value of the result should be taken?