Math
Master the quantitative skills used in science and healthcare: significant figures, unit conversions, proportions, functions, exponents, logarithms, statistics, and introductory calculus.
Statistics
Sign in to track progressBasic statistics summarize data and help interpret measurements, experimental results, and quality control data.
Mean (Average) The mean is the sum of all values divided by the number of values.
mean = (x₁ + x₂ + ... + xₙ) / n
Example: The mean of 10, 20, and 30 is (10 + 20 + 30) / 3 = 20.
Finding Totals from a Mean If you know the mean and the number of values, multiply to find the total.
Example: If the mean of 5 values is 12, the total sum is 5 × 12 = 60.
Median The median is the middle value when data are ordered. If there is an even number of values, the median is the average of the two middle values.
Comparing Mean and Median
The mean is affected by outliers (extreme values)
The median is more robust to outliers
For symmetric distributions, mean and median are similar
Basic Statistical Thinking Always consider sample size, variability, and whether the data are representative before drawing conclusions from a mean or median.
Key Points
- Mean is the sum of values divided by the count of values
- Total = mean × number of values
- Median is the middle value in ordered data
- The mean is sensitive to outliers; the median is less affected
- Consider context and sample size when interpreting averages