Common questions
Statistics FAQ
What should I study first in statistics?
Begin with data types, populations and samples, then learn measures of center and spread. Probability and standardized scores are easier to interpret once those foundations are clear.
Is statistics the same as probability?
No. Probability starts with a model and reasons about possible outcomes. Statistics starts with observed data and describes the data or uses them to learn about a wider population.
Why do sample and population formulas differ?
They answer different questions. A population formula describes every member of the group of interest. A sample formula uses observed data to estimate an unknown population quantity, which changes the variance denominator from n to n minus 1.
Where should I check notation and formula conditions?
Use the statistics formula sheet. It defines the symbols, separates sample and population notation, and states restrictions such as a positive standard deviation or a nonzero conditioning probability.