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Section 11.1 The Chi-square Distribution

Figure 11.1.1.
Chi-square Distribution (Made in GeoGebra by Chris Rosenthal)

Investigation 11.1.1.

(a)

    The \(\chi^2\) distribution curves are not symmetric, but instead are .....
  • positively skewed
  • negatively skewed

(b)

    As the degrees of freedom increases, the skewness .....
  • decreases
  • increases
  • stays the same

(c)

    The area under the curve is equal to .....
  • 0
  • \(1/2\)
  • 1
  • 2

(d)

    All \(\chi^2\) values are greater than or equal to .....
  • 0
  • 1
  • \(1/2\)
  • 2
We can use Table 8 in Appendix A of your book to find critical \(\chi^2\) values. The notation for these is \(\chi^2_{\alpha,df}\text{.}\)
  1. Find the desired significance level, \(\alpha\text{,}\) across the top of the table.
  2. Locate \(df\) along the left of the table.
We can also find critical \(\chi^2\)-values using the Excel command
\begin{equation*} CHISQ.INV.RT \end{equation*}

Exercise 11.1.2.

Find the following critical \(\chi^2\)-values:

(a)

\(\chi^2_{0.10,5}\)
Answer.
\(\approx 9.236\)

(b)

\(\chi^2_{0.975,24}\)
Answer.
\(\approx 12.401\)

(c)

\(\chi^2_{0.01,19}\)
Answer.
\(\approx 36.191\)

(d)

\(\chi^2_{0.90,10}\)
Answer.
\(\approx 4.865\)