How many large objects there are? How many of them are red?
8/25
Practice makes perfect
The probability that an event will occur, given that another event has already occurred, is called a conditional probability. Since we want to know the conditional probability of selecting a red object given that it is large, let's highlight the number of large red objects and the total number of large objects in the given two-way frequency table.
Large
Small
Totals
Blue
17
3
20
Red
8
12
20
Totals
25
15
40
The condition that the object selected is large limits the total outcomes to the 25. Of those 25 objects, 8 are red.
P(red | large)&=Large red/Large [1em]
P(red | large)&=8/25
