The problem asks us to compute the line of best fit (regression line) predicting success (denoted by $Y$) from study times (denoted by $X$). We are given the following summary statistics: Mean of $X$, $\bar{X} = 1.61$ Standard deviation of $X$, $s_x = 1.12$ Mean of $Y$, $\bar{Y} = 2.95$ Standard deviation of $Y$, $s_y = 0.99$ Correlation coefficient, $r = 0.65$

Probability and StatisticsRegressionLine of Best FitCorrelation CoefficientStatistical Analysis
2025/5/8

1. Problem Description

The problem asks us to compute the line of best fit (regression line) predicting success (denoted by YY) from study times (denoted by XX). We are given the following summary statistics:
Mean of XX, Xˉ=1.61\bar{X} = 1.61
Standard deviation of XX, sx=1.12s_x = 1.12
Mean of YY, Yˉ=2.95\bar{Y} = 2.95
Standard deviation of YY, sy=0.99s_y = 0.99
Correlation coefficient, r=0.65r = 0.65

2. Solution Steps

The equation for the line of best fit is given by:
Y=a+bXY = a + bX
where bb is the slope and aa is the y-intercept.
First, we calculate the slope bb using the formula:
b=rsysxb = r \cdot \frac{s_y}{s_x}
Plugging in the given values:
b=0.650.991.12=0.650.88392857140.5745535714b = 0.65 \cdot \frac{0.99}{1.12} = 0.65 \cdot 0.8839285714 \approx 0.5745535714
Next, we calculate the y-intercept aa using the formula:
a=YˉbXˉa = \bar{Y} - b \cdot \bar{X}
Plugging in the given values:
a=2.950.57455357141.61=2.950.925031252.02496875a = 2.95 - 0.5745535714 \cdot 1.61 = 2.95 - 0.92503125 \approx 2.02496875
Rounding aa and bb to two decimal places, we have a2.02a \approx 2.02 and b0.57b \approx 0.57.
So, the line of best fit is approximately:
Y=2.02+0.57XY = 2.02 + 0.57X

3. Final Answer

The equation of the line of best fit is Y=2.02+0.57XY = 2.02 + 0.57X.

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