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The chi-square statistic is given for a test for association, along with the two-way table showing the observed and expected counts.

\begin{tabular}{|l|lll|}
\hline
& A & \multicolumn{1}{|l}{B} & C \\
\hline
1 & [tex]$34(41.4)$[/tex] & [tex]$34(31.4)$[/tex] & [tex]$32(27.2)$[/tex] \\
2 & [tex]$25(41.4)$[/tex] & [tex]$51(31.4)$[/tex] & [tex]$24(27.2)$[/tex] \\
3 & [tex]$148(124.2)$[/tex] & [tex]$72(94.2)$[/tex] & [tex]$80(81.6)$[/tex] \\
\hline
\end{tabular}

Chi-square statistic [tex]$= 31.316$[/tex]

(a) What are the degrees of freedom for the test?

Degrees of freedom [tex]$= \square$[/tex]

(b) What is the [tex]$p$[/tex]-value?

[tex]$p$[/tex]-value [tex]$= \square$[/tex]


Sagot :

Sure, let's walk through the steps for solving this problem.

### Step-by-Step Solution:

#### (a) Degrees of Freedom Calculation:
To calculate the degrees of freedom for a chi-square test of independence, we use the formula:
[tex]\[ \text{Degrees of freedom} = (r - 1) \times (c - 1) \][/tex]
where [tex]\( r \)[/tex] is the number of rows and [tex]\( c \)[/tex] is the number of columns in the table.

From the given table:

1. [tex]\( r = 3 \)[/tex] (since there are 3 rows)
2. [tex]\( c = 3 \)[/tex] (since there are 3 columns)

Plugging in these values:
[tex]\[ \text{Degrees of freedom} = (3 - 1) \times (3 - 1) = 2 \times 2 = 4 \][/tex]

So, the degrees of freedom is:
[tex]\[ \text{Degrees of freedom} = 4 \][/tex]

#### (b) Calculating the p-value:
To find the p-value, we use the chi-square distribution with the chi-square statistic provided.

We're given:
- Chi-square statistic [tex]\( \chi^2 = 31.316 \)[/tex]
- Degrees of freedom [tex]\( \text{df} = 4 \)[/tex]

Looking up the p-value for the chi-square statistic with these degrees of freedom using chi-square distribution tables or a statistical software, we get:
[tex]\[ p\text{-value} \approx 2.639002855242545 \times 10^{-6} \][/tex]

Therefore, the p-value is:
[tex]\[ p\text{-value} \approx 2.639002855242545 \times 10^{-6} \][/tex]

### Final Answers:
(a) Degrees of freedom: [tex]\( \boxed{4} \)[/tex]

(b) p-value: [tex]\( \boxed{2.639002855242545 \times 10^{-6}} \)[/tex]