Quote from: alancalverd
the probability of a OR b is Pa + Pb...assuming that events a and b are mutually exclusive.
If a and b are independent events then you can get wrong answers.
For example if Pa=probability of rain today in the UK =70% (pardon my cynicism!)
Pb = probability that Coronavirus will be mentioned in the Newspaper = 99.99%
Then Pa + Pb = 70% + 99.99% = 170% (not possible)