Question

The table below gives the typical number of days of rainfall in Spring and Fall in Death Valley, California. Spring (Event S) Fall (Event F) Rain (Event R) 7 6 No Rain or Dry (Event D) 115 116 On average, what is the approximate percent chance of rainfall on a given day in Spring or Fall in Death Valley? 4.9% 5.3% 5.6% 6.0%

Answer 1

The table of the problem would look like this:
Spring (Event S) Fall (Event F) total
Rain (Event R) 7 6 13
No Rain (Event D) 115 116 231

In this question, you asked the probability of "rain" in either "Spring" or "Fall". Since the condition for the time is 2, you need to sum the event. The total event of rain would be 7+6= 13. The total event of no rain would be 115+116= 231
The chance of rain would be: 13/ (231+13) *100% = 5.327%