Probability and Statistics — Answer Key
Part A: Multiple Choice
Circle the best answer for each question.
1. A bag has 3 red and 2 blue marbles. What is P(red)?
A) 3/5
B) 2/5
C) 1/2
D) 1/5
Three red over five total marbles gives a probability of three fifths.
2. A bag has 3 red and 2 blue marbles. If you add 5 more red marbles, what is the new P(red)?
A) 3/5
B) 8/10
C) 5/10
D) 2/10
Eight red marbles over ten total marbles equals eight tenths or four fifths.
3. A line plot shows X marks at 2(2), 3(3), 4(1). What is the mode?
A) 2
B) 4
C) 3
D) 9
The value three has three X marks, the largest count on the plot.
4. A bar graph shows 4, 6, 8, 10, 12 books read. What is the mean?
A) 6
B) 10
C) 12
D) 8
The total forty divided by five categories gives an average of eight books.
Part B: Fill in the Blank
Write the correct answer on each line.
1. A bag has 4 green and 6 yellow marbles. P(green) = 4/10.
Four green over ten total marbles equals four tenths or two fifths.
2. Remove 2 yellow marbles from the same bag. New P(green) = 4/8.
Four green over eight total marbles simplifies to one half exactly.
3. A line plot has X's at 1(2), 2(4), 3(2), 4(2). The mean is 2.4.
Total twenty-four divided by ten data points equals two point four exactly.
4. The same line plot has a median of 2.
Values five and six are both two, so the median averages to two.
5. A bar graph shows quiz scores 7, 8, 8, 9, 10. The range is 3.
Maximum ten minus minimum seven gives a range of exactly three.