How many blue objects there are? How many of them are small?
3/20
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 small object given that it is blue, let's highlight the number of small blue objects and the total number of blue 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 blue limits the total outcomes to the 20. Of those 20 objects, 3 are small.
P(small | blue)&=Small blue/Blue [1em]
P(small | blue)&=3/20
