Probability and Data — Answer Key
Part A: Fix the Sentence
Each sentence has an error. Rewrite it correctly on the line.
1. Fix the sentence:
Flipping a coin and getting heads is impossible.
Corrected: Flipping a coin and getting heads is likely.
Heads is one of two equal outcomes, so it is likely, not impossible.
2. Fix the sentence:
Pulling a red marble from a bag of only blue marbles is certain.
Corrected: Pulling a red marble from a bag of only blue marbles is impossible.
An event with zero matching items in the set is impossible to occur.
3. Fix the sentence:
Rolling a number less than 7 on a standard die is unlikely.
Corrected: Rolling a number less than 7 on a standard die is certain.
All six outcomes are below 7, so the event must happen every time.
Part B: Fill in the Blank
Write the missing word or number on each line.
1. An event that will definitely happen is called certain.
Certain events have a probability of one because they always happen.
2. An event that cannot ever happen is called impossible.
Impossible events have a probability of zero and never occur.
3. On a tally chart, four straight marks plus one slash equals 5.
Tally marks are grouped in fives so totals are easy to count quickly.
4. If a bar reaches the number 8 on a bar graph, the count is 8.
The height of a bar matches the value shown on the graph scale.
Part C: Short Answer
Answer each question in one or two complete sentences.
1. Why is rolling a 3 on a six-sided die unlikely but not impossible?
Sample answer: Only one face shows 3 out of six faces, so it can happen but probably will not on any single roll.
Unlikely events have few matching outcomes compared to the total possible outcomes.
2. How does a tally chart help you read data quickly?
Sample answer: Tally marks group counts in fives, so you can skip-count by fives and add the leftover marks to find totals.
Grouping by fives reduces counting steps and lowers the chance of mistakes.