Determine the regression line for predicting a woman's bone density based on her age.
Calculate the means of \( x \) and \( y \).
The mean of \( x \) (ages) is given by \( \bar{x} = \frac{1}{n} \sum_{i=1}^{n} x_i = 55.8 \). The mean of \( y \) (bone densities) is \( \bar{y} = \frac{1}{n} \sum_{i=1}^{n} y_i = 337.8 \).
Calculate the correlation coefficient \( r \).
The correlation coefficient is calculated as \( r = -0.9192 \).
Calculate the slope \( \beta \).
The numerator for \( \beta \) is \( \sum_{i=1}^{n} x_i y_i - n \bar{x} \bar{y} = 93676 - 5 \cdot 55.8 \cdot 337.8 = -570.2 \). The denominator for \( \beta \) is \( \sum_{i=1}^{n} x_i^2 - n \bar{x}^2 = 15933 - 5 \cdot 55.8^2 = 364.8 \). Thus, the slope is \( \beta = \frac{-570.2}{364.8} = -1.563 \).
Calculate the intercept \( \alpha \).
The intercept is calculated as \( \alpha = \bar{y} - \beta \bar{x} = 337.8 - (-1.563) \cdot 55.8 = 425.0181 \).
Formulate the regression line equation.
The line of best fit is given by \( y = 425.0181 - 1.563x \).
The regression line is \( y = 425.0181 - 1.563x \).
Determine the change in the dependent variable \( \hat{y} \) when the independent variable \( x \) is increased by one unit.
Identify the change in \( \hat{y} \).
According to the model, if the value of the independent variable \( x \) is increased by one unit, the change in the dependent variable \( \hat{y} \) is equal to the slope \( \beta \), which is \( -1.563 \).
The change in \( \hat{y} \) is \( -1.563 \).
The regression line is \( y = 425.0181 - 1.563x \).
The change in \( \hat{y} \) when \( x \) is increased by one unit is \( -1.563 \).