Topic A: Statistics & Graphs
Center, spread, and reading data displays.
01 — Mean, Median, Mode & Range
Mean, Median, Mode & Range
These four numbers describe a list of data.
- Mean: the average. Add them up, divide by how many.
- Median: the middle number after putting them in order. If two middles, average them.
- Mode: the number that shows up most.
- Range: biggest minus smallest.
Example: 3, 5, 5, 8, 9 → mean 6, median 5, mode 5, range 6.
Practice — Mean, Median, Mode & Range
Q1 · Short Answer
Find the mean of 4, 8, 10, 6.
Q2 · Short Answer
Find the median of 12, 3, 7, 9, 5.
02 — Charts & Graphs
Reading Charts & Graphs
The GED loves bar graphs, line graphs, circle graphs, and tables. Read the title and labels first!
- Bar graph: compares groups.
- Line graph: shows change over time.
- Circle (pie) graph: shows parts of a whole; the parts add to 100%.
- Scatter plot: shows if two things are related (positive, negative, or no trend).
Example: A pie chart shows 25% of 200 students walk to school. 0.25 × 200 = 50 students.
Practice — Reading Charts & Graphs
Q3 · Multiple Choice
Which graph is best for showing temperature changes over a week?
Q4 · Short Answer
A circle graph shows 40% of a $500 budget is rent. How many dollars is rent?
Topic B: Probability
Chance, counting, and combined events.
03 — Simple Probability
Simple Probability
Probability is how likely something is, from 0 (never) to 1 (always).
- Probability: P = (ways you want) ÷ (total ways).
- As a percent: 1/4 = 0.25 = 25%.
- Not happening: P(not A) = 1 − P(A).
- Fair coin: P(heads) = 1/2. Fair die: P(any one number) = 1/6.
Example: A bag has 3 red and 7 blue marbles. P(red) = 3/10.
Practice — Simple Probability
Q5 · Multiple Choice
You roll a fair die. What is the probability of rolling an even number?
Q6 · Short Answer
The chance of rain is 0.3. What is the chance it does NOT rain? (as a decimal)
04 — Counting & Combined Events
Counting & Combined Events
When two things happen, multiply to count all the ways.
- Counting principle: 3 shirts and 4 pants make 3 × 4 = 12 outfits.
- Independent events: one doesn't change the other. P(A and B) = P(A) × P(B).
- Permutation: order matters (1st, 2nd, 3rd place).
- Combination: order doesn't matter (picking a team).
Example: Flip a coin twice. P(two heads) = 1/2 × 1/2 = 1/4.
Practice — Counting & Combined Events
Q7 · Short Answer
A café has 4 sandwiches and 3 drinks. How many sandwich-and-drink combos are there?
Q8 · Multiple Choice
You flip a coin and roll a die. What is P(heads and a 6)?