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Manufacturers are testing a die to make sure that it is fair (has a uniform distribution). They roll the die 78 times and record the outcomes in the table below. They conduct a chi-square Goodness-of-Fit hypothesis test at the [tex]$1\%$[/tex] significance level.

\begin{tabular}{|c|c|c|c|c|c|c|}
\hline Outcome & 1 & 2 & 3 & 4 & 5 & 6 \\
\hline Expected & 13 & 13 & 13 & 13 & 13 & 13 \\
\hline Observed & 7 & 10 & 14 & 16 & 9 & 22 \\
\hline
\end{tabular}

(a) The null and alternative hypotheses are:
- [tex]$H_0$[/tex] : The die has the uniform distribution.
- [tex]$H_a$[/tex] : The die does not have the uniform distribution.

(b) Compute the test statistic, rounded to three decimal places.

Provide your answer below:
Test Statistic [tex]$=$[/tex] [tex]$\square$[/tex]


Sagot :

To conduct a chi-square Goodness-of-Fit test, we follow a standard methodology:

1. Set up the hypotheses:
- Null hypothesis ([tex]\( H_0 \)[/tex]): The die has a uniform distribution.
- Alternative hypothesis ([tex]\( H_a \)[/tex]): The die does not have a uniform distribution.

2. Observed and expected frequencies:
- Observed counts: [tex]\([7, 10, 14, 16, 9, 22]\)[/tex]
- Expected counts: [tex]\([13, 13, 13, 13, 13, 13]\)[/tex]

3. Calculate the chi-square test statistic ([tex]\( \chi^2 \)[/tex]):
[tex]\[ \chi^2 = \sum \frac{(O_i - E_i)^2}{E_i} \][/tex]
where [tex]\( O_i \)[/tex] is the observed frequency and [tex]\( E_i \)[/tex] is the expected frequency.

4. Compute the individual components:
- For outcome 1: [tex]\(\frac{(7 - 13)^2}{13} = \frac{36}{13}\)[/tex]
- For outcome 2: [tex]\(\frac{(10 - 13)^2}{13} = \frac{9}{13}\)[/tex]
- For outcome 3: [tex]\(\frac{(14 - 13)^2}{13} = \frac{1}{13}\)[/tex]
- For outcome 4: [tex]\(\frac{(16 - 13)^2}{13} = \frac{9}{13}\)[/tex]
- For outcome 5: [tex]\(\frac{(9 - 13)^2}{13} = \frac{16}{13}\)[/tex]
- For outcome 6: [tex]\(\frac{(22 - 13)^2}{13} = \frac{81}{13}\)[/tex]

5. Sum these components:
[tex]\[ \chi^2 = \frac{36}{13} + \frac{9}{13} + \frac{1}{13} + \frac{9}{13} + \frac{16}{13} + \frac{81}{13} \][/tex]
[tex]\[ \chi^2 = \frac{36 + 9 + 1 + 9 + 16 + 81}{13} = \frac{152}{13} \approx 11.692 \][/tex]

So, the test statistic [tex]\( \chi^2 \)[/tex] rounded to three decimal places is:
[tex]\[ \boxed{11.692} \][/tex]
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