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Assume that variables [tex]$x$[/tex] and [tex]$y$[/tex] have a significant correlation, and that the line of best fit has been calculated as [tex]$\hat{y}=8+2.2x$[/tex]. One observation is [tex]$(11,33.7)$[/tex].

1. What is the predicted value of [tex]$y$[/tex] for the value [tex]$x=11$[/tex]? [tex]$\square$[/tex]
2. What is the residual for the value [tex]$x=11$[/tex]? [tex]$\square$[/tex]
3. What is the best interpretation for the residual?
A. The value 33.7 is below the average value for [tex]$x$[/tex] when [tex]$y=33.7$[/tex].
B. The value 11 is above the average value for [tex]$y$[/tex] when [tex]$y=33.7$[/tex].
C. The value 33.7 is below the average value for [tex]$y$[/tex] when [tex]$x=11$[/tex].
D. The value 33.7 is above the average value for [tex]$y$[/tex] when [tex]$x=11$[/tex].


Sagot :

To solve this problem, follow these steps:

### Step 1: Determine the Predicted Value of [tex]\( y \)[/tex]

Given the line of best fit [tex]\(\hat{y} = 8 + 2.2x\)[/tex], we need to find the predicted value of [tex]\( y \)[/tex] when [tex]\( x = 11 \)[/tex].

[tex]\[ \hat{y} = 8 + 2.2 \times 11 \][/tex]

Calculate:

[tex]\[ \hat{y} = 8 + 24.2 = 32.2 \][/tex]

So, the predicted value of [tex]\( y \)[/tex] for [tex]\( x = 11 \)[/tex] is 32.2.

### Step 2: Calculate the Residual

The residual is the difference between the observed value and the predicted value. The observed value of [tex]\( y \)[/tex] when [tex]\( x = 11 \)[/tex] is 33.7.

[tex]\[ \text{Residual} = \text{Observed } y - \text{Predicted } y = 33.7 - 32.2 \][/tex]

Calculate:

[tex]\[ \text{Residual} = 1.5 \][/tex]

So, the residual for the value [tex]\( x = 11 \)[/tex] is 1.5.

### Step 3: Interpret the Residual

To interpret the residual, we need to compare the observed value with the predicted value:
- If the observed value is greater than the predicted value, it indicates that the observed value is above the average value predicted by the model for that particular [tex]\( x \)[/tex] value.
- If the observed value is less than the predicted value, it indicates that the observed value is below the average value predicted by the model for that particular [tex]\( x \)[/tex] value.

In this case, the observed value of [tex]\( y = 33.7 \)[/tex] is greater than the predicted value of [tex]\( y = 32.2 \)[/tex].

Hence:

- The value 33.7 is above the average value for [tex]\( y \)[/tex] when [tex]\( x = 11 \)[/tex].

### Summary of Answers:

- Predicted value of [tex]\( y \)[/tex] for [tex]\( x = 11 \)[/tex]: 32.2
- Residual for the value [tex]\( x = 11 \)[/tex]: 1.5
- Best interpretation for the residual: The value 33.7 is above the average value for [tex]\( y \)[/tex] when [tex]\( x = 11 \)[/tex]