Statistics

• Equation for relative sampling error, with proportion of cases (p) instead of mean:

  $r =$$\pm t_{a/2} \cdot \sqrt{\frac{1-p}{p \cdot n} \left(1-\frac{n}{N}\right)}$
• Equation to compute relative sampling accuracy:

  $r =$$\pm \frac{t_{a/2}S_x}{\sqrt{n}\overline X}\cdot\sqrt{1-\frac{n}{N}}$
• What is a variance?

  Means how possible values spread around the value. Usually use mean as a main value.
• How co compute variance (for a sample set)?

  $\sigma^2 =$$\frac{\Sigma_{i=1}^n(x_i-\bar x)^2}{n-1}$
• How to compute variance for a population set?


  $\sigma^2 =$$\frac{\Sigma_{i=1}^n(x_i-\bar x)^2}{n}$
• Simplified equation for standard error, with given population's st.deviation:

  $st.Error =$$\frac{\sigma}{\sqrt{n}}$
• Simplified equation for standard error, with sample standard deviation:

  $St.Error =$$\frac{s}{\sqrt{n}}$