In a political science class, the teacher gives a midterm exam and a final. The association between midterm and final scores is linear. The summary statistics are shown below. Midterm Mean=75, Midterm Standard Deviation=10 Final Mean=75, Final Standard Deviation=10 r=0.8 According to the regression equation, for a student who gets 85 on the midterm (one standard deviation above average) what is the predicted final exam grade?

Question

contestada

Respuesta :

MrRoyal MrRoyal · Answer 1 · 2021-06-23T21:16:19+02:00

Answer:

The predicted final exam grade is 83

Step-by-step explanation:

Given

[tex]\bar x = 75[/tex] -- midterm mean

[tex]\sigma_x = 10[/tex] --- midterm standard deviation

[tex]\mu =75[/tex] --- final mean

[tex]\sigma = 10[/tex] --- final standard deviation

[tex]r = 0.8[/tex]

Required

The predicted final grade of student who score 85 in midterm

The prediction is represented as:

[tex]y = \alpha + \beta x[/tex]

Where:

[tex]\beta = r * \frac{\sigma}{\sigma_x}[/tex]

[tex]\beta = 0.8 * \frac{10}{10}[/tex]

[tex]\beta = 0.8 * 1[/tex]

[tex]\beta = 0.8[/tex]

and

[tex]\alpha = \mu - r * \bar x[/tex]

[tex]\alpha = 75- 0.8 * 75[/tex]

[tex]\alpha = 75- 60[/tex]

[tex]\alpha = 15[/tex]

So:

[tex]y = \alpha + \beta x[/tex]

[tex]y = 15 + 0.8x[/tex]

For a student who gets 85, the prediction is:

[tex]y = 15 + 0.8*85[/tex]

[tex]y = 15 + 68[/tex]

[tex]y = 83[/tex]