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BA II Plus: Mean and Variance Step by Step
Calculate mean and variance from a data set using BA II Plus statistics outputs.
TL;DR
Use DATA and STAT for the mean and standard deviation, then square the standard deviation when variance is required.
Formula Reference
Variance
Variance = standard deviation^2Use sample or population standard deviation depending on the question.
BA II Plus Keystrokes
- 2nd DATA
- 2nd CLR WORK
- Enter observations
- 2nd STAT
- Read x-bar for mean
- Read Sx, then press x^2 for sample variance
Worked Example
- Problem: Observations are 2, 4, and 6.
- Mean = 4.
- Sample standard deviation = 2, so sample variance = 4.
Common Mistakes
- Forgetting to square standard deviation for variance.
- Using old data from a previous problem.
- Using sample outputs for a full population question.
Related Guides
- BA II Plus: Standard Deviation Step by Step - Use the BA II Plus DATA and STAT worksheets to compute sample standard deviation.
- CFA Level I Quantitative Methods Calculation Guide - Formulas, examples, and calculator workflows for CFA Level I quantitative methods.
- CFA Level I Quantitative Methods Formula Sheet - Public formula sheet for CFA Level I quantitative methods calculations.