Data Analysis & Probability
Study Guide
Data analysis and statistics make up about 20% of the GED Math test. You need to calculate measures of center, read graphs and charts, and understand basic probability.
1Measures of Central Tendency
Mean (average): Add all values, divide by count. Median: Middle value when sorted. Mode: Most frequent value. Range: Largest minus smallest.
Examples:
•Data: 3, 5, 7, 7, 8 → Mean = 30/5 = 6, Median = 7, Mode = 7, Range = 5
•Data: 2, 4, 6, 8 → Mean = 20/4 = 5, Median = (4+6)/2 = 5, No mode, Range = 6
2Probability
Probability = favorable outcomes / total outcomes. It ranges from 0 (impossible) to 1 (certain). To convert to percent, multiply by 100.
Examples:
•Rolling a 3 on a die: P = 1/6 ≈ 16.7%
•Drawing a red card from a deck: P = 26/52 = 1/2 = 50%
•P(not A) = 1 - P(A)
3Reading Graphs and Charts
The GED frequently asks you to interpret bar graphs, line graphs, pie charts, and scatter plots. Always read the title, labels, and scale carefully.
Examples:
•Bar graph: Compare heights of bars to compare quantities
•Line graph: Look at the trend (increasing, decreasing, or steady)
•Pie chart: Each slice shows a percentage of the whole
Key Formulas to Remember
1Mean = sum of all values / number of values
2Probability = favorable outcomes / total outcomes
3P(not A) = 1 - P(A)
Test-Taking Tips
On graph questions, always check the scale on the axes — they may not start at 0.
For median with an even number of values, average the two middle numbers.
Probability questions often use 'not' — remember P(not) = 1 - P(event).