EXAMPLE 2 Determining unusual or likely outcomes

For the following probabilities, determine the meaning of the indicated probability:

  1. The weatherman said that the chance of rain tonight was near 100%.
  2. The coach said that after that last loss, the team had no chance to make the playoffs.
  3. The doctor said that the chance of a negative reaction to the planned procedure was 3%.

Solution

  1. A value of near 100% is near 1. Therefore, it is nearly certain to occur that we will have rain tonight.
  2. No chance means a probability equal to zero. Therefore, it cannot occur that the team will make the playoffs.
  3. The chance of a negative reaction is 3%, or 0.03. This probability is low (for example, below a certain threshold, such as 0.05), so we conclude that it would be unusual for a negative reaction to the planned procedure to occur.

NOW YOU CAN DO

Exercises 17–20.