How many red objects there are? How many of them are large?
2/5
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 large object given that it is red, let's highlight the number of large red objects and the total number of red 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 red limits the total outcomes to the 20. Of those 20 objects, 8 are large.
P(large | red)&=Large red/Red [1em]
P(large | red)&=8/20=2/5
