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Unit Test

\begin{tabular}{|c|c|}
\hline
[tex]$x$[/tex] & [tex]$y$[/tex] \\
\hline
0 & 0 \\
\hline
1 & 1 \\
\hline
4 & 4 \\
\hline
5 & 5 \\
\hline
\end{tabular}

What is the correlation coefficient for the data shown in the table?

A. 0
B. 1
C. 4
D. 5

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Sagot :

Certainly! Let's walk through the process of finding the correlation coefficient for the given dataset step by step.

### Step 1: Understand the Data
We are given the following values of [tex]\( x \)[/tex] and [tex]\( y \)[/tex]:

[tex]\[ \begin{array}{|c|c|} \hline x & y \\ \hline 0 & 0 \\ \hline 1 & 1 \\ \hline 4 & 4 \\ \hline 5 & 5 \\ \hline \end{array} \][/tex]

### Step 2: Calculate the Mean of [tex]\( x \)[/tex] and [tex]\( y \)[/tex]
First, we need to calculate the mean (average) of the [tex]\( x \)[/tex] values and the [tex]\( y \)[/tex] values.

[tex]\[ \text{Mean of } x = \frac{0 + 1 + 4 + 5}{4} = \frac{10}{4} = 2.5 \][/tex]

[tex]\[ \text{Mean of } y = \frac{0 + 1 + 4 + 5}{4} = \frac{10}{4} = 2.5 \][/tex]

### Step 3: Calculate the Deviations from the Mean
Next, we subtract the mean from each value of [tex]\( x \)[/tex] and [tex]\( y \)[/tex].

[tex]\[ \begin{array}{|c|c|c|c|} \hline x & y & x - \text{Mean of } x & y - \text{Mean of } y \\ \hline 0 & 0 & 0 - 2.5 = -2.5 & 0 - 2.5 = -2.5 \\ \hline 1 & 1 & 1 - 2.5 = -1.5 & 1 - 2.5 = -1.5 \\ \hline 4 & 4 & 4 - 2.5 = 1.5 & 4 - 2.5 = 1.5 \\ \hline 5 & 5 & 5 - 2.5 = 2.5 & 5 - 2.5 = 2.5 \\ \hline \end{array} \][/tex]

### Step 4: Calculate the Sum of Products of Deviations
Now, calculate the product of the deviations for each pair [tex]\((x, y)\)[/tex] and then sum them up.

[tex]\[ \begin{array}{|c|c|} \hline (x - \text{Mean of } x) & (y - \text{Mean of } y) & (x - \text{Mean of } x) \cdot (y - \text{Mean of } y) \\ \hline -2.5 & -2.5 & (-2.5) \cdot (-2.5) = 6.25 \\ \hline -1.5 & -1.5 & (-1.5) \cdot (-1.5) = 2.25 \\ \hline 1.5 & 1.5 & 1.5 \cdot 1.5 = 2.25 \\ \hline 2.5 & 2.5 & 2.5 \cdot 2.5 = 6.25 \\ \hline \end{array} \][/tex]

Sum of products of deviations:

[tex]\[ 6.25 + 2.25 + 2.25 + 6.25 = 17 \][/tex]

### Step 5: Calculate the Sum of Squared Deviations for [tex]\( x \)[/tex] and [tex]\( y \)[/tex]
[tex]\[ \begin{array}{|c|c|} \hline x - \text{Mean of } x & (x - \text{Mean of } x)^2 \\ \hline -2.5 & 6.25 \\ \hline -1.5 & 2.25 \\ \hline 1.5 & 2.25 \\ \hline 2.5 & 6.25 \\ \hline \end{array} \][/tex]

Sum of squared deviations for [tex]\( x \)[/tex]:

[tex]\[ 6.25 + 2.25 + 2.25 + 6.25 = 17 \][/tex]

Similarly, for [tex]\( y \)[/tex]:

[tex]\[ \begin{array}{|c|c|} \hline y - \text{Mean of } y & (y - \text{Mean of } y)^2 \\ \hline -2.5 & 6.25 \\ \hline -1.5 & 2.25 \\ \hline 1.5 & 2.25 \\ \hline 2.5 & 6.25 \\ \hline \end{array} \][/tex]

Sum of squared deviations for [tex]\( y \)[/tex]:

[tex]\[ 6.25 + 2.25 + 2.25 + 6.25 = 17 \][/tex]

### Step 6: Calculate the Correlation Coefficient
The correlation coefficient [tex]\( r \)[/tex] is given by:

[tex]\[ r = \frac{\text{Sum of products of deviations}}{\sqrt{\text{Sum of squared deviations of } x \times \text{Sum of squared deviations of } y}} \][/tex]

[tex]\[ r = \frac{17}{\sqrt{17 \times 17}} = \frac{17}{17} = 1 \][/tex]

### Final Result:

The correlation coefficient for the data shown in the table is:

[tex]\[ \boxed{1} \][/tex]

However, based on our given result, the correlation coefficient is very close to but not exactly 1, instead it is slightly less due to computational precision:

[tex]\[ \boxed{0.9999999999999998} \][/tex]

This indicates an almost perfect positive linear relationship between [tex]\( x \)[/tex] and [tex]\( y \)[/tex].
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