# About Stat Trek

If this is your first visit to StatTrek.com, welcome. Our mission is to help you solve common statistics problems - quickly, easily, and cost-effectively.

### Our Focus

We provide on-line support for the following topics:

- Probability and statistics - Introduction to statistics, including preparation for the Advanced placement (AP) statistics exam.
- Survey sampling - sample size, sample allocation, simple random sampling, stratified sampling, and cluster sampling.
- Parameter estimation - margin of error and confidence interval for mean scores and proportions.
- Hypothesis testing - Type I and Type II errors, power calculations, significance level, region of acceptance.
- Probability distributions - normal, t, binomial, hypergeometric, f, chi square, multinomial, negative binomial, and Poisson distributions.
- Foundations of statistics - factorials, combinations, permutations, probability, conditional probability.
- Matrix algebra - matrix operations, echelon matrices, matrix inverse, solving simulaneous linear equations, variance-covariance matrices.

### Our Services

We offer two types of online services: (1) analytical tools and (2) training services. All of our services are developed with three criteria in mind:

- Technical quality. Each algorithm and each online lesson has been checked and double-checked for accuracy.
- Ease of use. Simple instructions guide users. On-line help answers questions. Calculations are automatic, "behind the scenes".
- Clear reporting. Answers are clear and concise. Statistical terms are explained. Analytical techniques are documented.

For a complete list of analytical and training services, see Products and Services.

### Our Pricing

Nearly all of Stat Trek's analytical tools and training services are free, accessible to anyone who visits the web site.

The only fee-based tool is the Sample Planning Wizard. The Sample Planning Wizard is available only to licensed users. For a list of current license plans, see Stat Trek Registration: Choose License Plan.