In: Statistics and Probability
The following data give the number of hours 55 students spent studying and their corresponding grades on their midterm exams.
Hours Studying | 2 | 5 | 5 | 5 | 5 |
---|---|---|---|---|---|
Midterm Grades | 68 | 74 | 81 | 92 | 99 |
Step 4 of 5 :
Construct the 90% confidence interval for the slope. Round your answers to three decimal places.
X | Y | X2 | X * Y | Sxx =Σ (Xi - X̅ ) | Syy = Σ( Yi - Y̅ ) | Sxy = Σ (Xi - X̅ ) * (Yi - Y̅) | |
2 | 68 | 4 | 136 | 5.76 | 219.04 | 35.52 | |
5 | 74 | 25 | 370 | 0.36 | 77.44 | -5.28 | |
5 | 81 | 25 | 405 | 0.36 | 3.24 | -1.08 | |
5 | 92 | 25 | 460 | 0.36 | 84.64 | 5.52 | |
5 | 99 | 25 | 495 | 0.36 | 262.44 | 9.72 | |
Total | 22 | 414 | 104 | 1866 | 7.2 | 646.8 | 44.4 |
X̅ = Σ (Xi / n ) = 22/5 = 4.4
Y̅ = Σ (Yi / n ) = 414/5 = 82.8
Equation of regression line is Ŷ = a + bX
b = ( n Σ(XY) - (ΣX* ΣY) ) / ( n Σ X2 - (ΣX)2
)
b = ( 5 * 1866 - 22 * 414 ) / ( 5 * 104 - ( 22 )2)
b = 6.1667
a =( ΣY - ( b * ΣX ) ) / n
a =( 414 - ( 6.1667 * 22 ) ) / 5
a = 55.6667
Equation of regression line becomes Ŷ = 55.6667 + 6.1667
X
Slope = b = 6.1667
Confidence Interval
90% confidence interval is -3.613 < <
15.946