School Improvement in Maryland
Clarifications: Each clarification provides an explanation of the indicator/objective to help teachers better understand the concept. Classroom examples are often included to further illustrate the concept. While classroom examples could be shared with the students, the intended audience for the explanation/clarification is the classroom teacher-not the student. In addition, classroom examples may or may not reflect the assessment limits.

Standard 5.0 Knowledge of Probability

Topic B. Theoretical Probability

Indicator 1. Determine the probability of one simple event comprised of equally likely outcomes

Objective a. Express the probability as a fraction

Assessment limit: Use a sample space of no more than 6 outcomes

Clarification

Probability is the chance or likelihood of an event occurring. Theoretical probability describes the chance of an event occurring based on possible outcomes. For example, when flipping a coin, you could get heads or you could get tails. So the outcomes are heads or tails. An event is a specific set of outcomes, such as tails. A favorable outcome is one in the set of outcomes for which we want to find the probability.

  • When flipping a coin there is a 1/2 chance that you will get heads on a flip. Or this can be thought of as 1 out of 2 chances.

    geometric image

  • When rolling a number cube, the possible outcomes are 1, 2, 3, 4, 5, and 6. There are 6 possible outcomes. Rolling an even number is an event. Rolling a 2, or a 4, or a 6 is each a favorable outcome. What is the probability of rolling an even number? Since there are three favorable outcomes that could occur (2, 4, 6), and they are equally likely, the probability is 3/6.

  • A bag contains 6 marbles (2 red, 4 blue).

    What is the probability of picking a red marble? 2/6

    What is the probability of picking a blue marble? 4/6

    What is the probability of picking a yellow marble? 0/6

Note: Even though there are only 2 colors, there are six marbles. Therefore there are 6 outcomes.

Classroom Example 1

Connections within the content:

A bag contains 6 marbles. 2 are red and 4 are blue.

Which of the numbers below is the probability of picking a red marble?

  1. 3/6
  2. 2/4
  3. 2/6
  4. 4/6

Answer: C

Although the content of the item is essentially probability, the answer choices require that the student be able to express probabilities as fractions. Describing quantities as fractional parts is a skill within the content of number. When appropriate, connect number concepts to concepts within the other content strands to show how number concepts and operations need not be taught in isolation..
/instruction/clarification/mathematics/grade4/xml/5B1a.xml
Resources for Objective 5.B.1.a:
CLARIFICATIONS | Thinking Skills | Sample Assessments |