Statistical literacy is the ability to read numbers in news, ads, studies, and social media with careful judgment. It matters because percentages, averages, graphs, and risk claims can strongly shape decisions about health, money, school, and public policy. A statistically literate person asks what was measured, who was included, how large the sample was, and whether the conclusion really follows from the data.
Key Facts
- Percentage change = (new value - old value) / old value × 100%
- Mean = sum of all values / number of values
- Median = middle value when the data are ordered
- Range = maximum value - minimum value
- Margin of error gives a likely amount of random sampling error around an estimate.
- Correlation does not prove causation.
Vocabulary
- Statistical literacy
- The ability to understand, question, and use statistics in everyday information and decision making.
- Sample
- A sample is the group of people, objects, or measurements actually studied to learn about a larger population.
- Margin of error
- A margin of error describes how far a sample estimate may reasonably be from the true population value due to random sampling.
- Relative risk
- Relative risk compares the chance of an outcome in one group to the chance of that outcome in another group.
- Bias
- Bias is a systematic error that makes data or conclusions lean away from the truth.
Common Mistakes to Avoid
- Confusing percentage points with percent change: saying 20% rose to 30% is a 10% increase is wrong because it is a 10 percentage point increase and a 50% relative increase.
- Trusting an average without checking the spread: the mean can hide large differences or extreme values, so look for the median, range, or distribution when possible.
- Ignoring sample size and sampling method: a result from a tiny or biased sample may not represent the larger population, even if the graph looks professional.
- Treating correlation as causation: two variables moving together does not prove that one caused the other because a third variable or coincidence may explain the pattern.
Practice Questions
- 1 A product price rises from 50. What is the percent increase?
- 2 A poll of 1,000 voters finds that 54% support a proposal with a margin of error of 3 percentage points. What interval of support is suggested by the poll?
- 3 An advertisement says a supplement cuts risk by 50%, but the risk changes from 2 out of 1,000 people to 1 out of 1,000 people. Explain why both the relative risk and absolute risk should be considered.