Question

Taking a test i don’t know anything about please help

Answer 1

Answer:

See below for answers and explanations

Step-by-step explanation:

Problem 4:

The line of regression is $\hat y = a+bx$ where:

$a=\overline y-b \overline x$

$b=\frac{r*s_y}{s_x}$

We are given that $\overline y=75$, $s_y=8$, $\overline x=280$, $s_x=30$, and $r=0.60$, therefore our slope, $b$, is:

$b=\frac{r*s_y}{s_x}$

$b=\frac{(0.60)(8)}{30}$

$b=0.16$

Therefore, the slope of the regression line is 0.16, which can be used along with the values of $\overline y$ and $\overline x$ to find the constant $a$:

$a=\overline y-b \overline x$

$a=75-(0.16)(280)$

$a=30.2$

This means our final regression line is $\hat y = 30.2 + 0.16x$

Problem 5:

The slope, $b=0.16$, means that for every 1 point earned for a student's pre-exam total, their final exam score will increase by 0.16 points for each point they earned on the pre-exam.

Problem 6:

The y-intercept (or constant), $a=30.2$, means that if a student's pre-exam total were 0, then they would expect to get a 30.2 on the final exam.

Problem 7:

$R^{2}=(0.60)^{2}=0.36=36\%$

Problem 8:

The fraction of variability (aka. coefficient of determination), $R^2$, means that a certain proportion (or percentage) of the variance in the response variable can be explained by the explanatory variable. In context, this means that 36% of the variance in final exam scores can be explained by the pre-exam scores.