Introduction to Statistics
Probability
Example 1
What is the probability of simultaneously flipping three coins—a penny, a nickel, and a dime—and having all three land heads?
Using the classic theory, determine the ratio of the number of favorable outcomes to the number of total outcomes. Table 1 lists all possible outcomes.
There are eight different outcomes, only one of which is favorable (Outcome 1, all three coins landing heads); therefore, the probability of three coins landing heads is
, or 0.125.
What is the probability of exactly two of the three coins landing heads? Again, there are the eight total outcomes, but in this case only three favorable outcomes (outcomes 2, 3, and 5); thus, the probability of exactly two of three coins landing heads is
, or 0.375.
|
Outcome |
Penny |
Nickel |
Dime |
|---|---|---|---|
|
1 |
Head |
Head |
Head |
|
2 |
Head |
Head |
Tail |
|
3 |
Head |
Tail |
Head |
|
4 |
Head |
Tail |
Tail |
|
5 |
Tail |
Head |
Head |
|
6 |
Tail |
Head |
Tail |
|
7 |
Tail |
Tail |
Head |
|
8 |
Tail |
Tail |
Tail |
