Probability and Statistics — Answer Key
Part A: Fix the Sentence
Each sentence has an error. Rewrite it correctly on the line.
1. Fix the sentence:
On a spinner with 4 equal red sections, landing on red is unlikely.
Corrected: On a spinner with 4 equal red sections, landing on red is certain.
If all spinner sections are red, the spinner must always stop on red.
2. Fix the sentence:
The probability of rolling an even number on a six-sided die is 1/6.
Corrected: The probability of rolling an even number on a six-sided die is 1/2.
Three even faces over six total faces simplifies to one half exactly.
3. Fix the sentence:
Pulling a green marble from a bag of 5 red marbles is likely.
Corrected: Pulling a green marble from a bag of 5 red marbles is impossible.
With zero favorable outcomes the probability is zero, which is impossible.
Part B: Fill in the Blank
Write the missing word or number on each line.
1. On a spinner with 4 equal sections (1 blue, 3 yellow), P(yellow) = 3/4.
Three favorable yellow over four total equal sections gives three fourths.
2. Rolling an odd number (1, 3, or 5) on a standard die has probability 1/2.
Three odd outcomes over six total faces simplifies to one half exactly.
3. If 2 of 8 marbles are green, the probability of green is 1/4.
Two green marbles over eight total marbles simplifies to one fourth.
4. An event that probably will not happen is called unlikely.
Unlikely events have probability less than one half but more than zero.
Part C: Short Answer
Answer each question in one or two complete sentences.
1. A bag has 3 red and 7 blue marbles. Is drawing red likely or unlikely? Give the probability.
Sample answer: Drawing red is unlikely because only 3 of 10 marbles are red, so the probability is 3/10.
Three favorable outcomes over ten total means a probability less than one half.
2. Why is the probability of flipping heads or tails on a fair coin certain?
Sample answer: Every flip lands on either heads or tails, so the event always happens and the probability is 1.
When favorable outcomes equal total outcomes, the probability equals exactly one.