SUMMARY OUTPUT cov (X,Y) -2487708.147 Regression Statistics Sx 6572.761629 Multi
ID: 3261024 • Letter: S
Question
SUMMARY OUTPUT
cov (X,Y) -2487708.147
Regression Statistics
Sx 6572.761629
Multiple R 0.793745367
Sy 476.837435
R Square
Adjusted R Square 0.62625652
Standard Error
Observations 100
ANOVA
df SS MS F Significance F
Regression 1 14182026.33 14182026.33
Residual 98 8327993.674 84979.52728
Total 99 22510020
Coefficients Standard Error t Stat P-value Lower 95% Upper 95% Lower 80.0% Upper 80.0%
Intercept 16887.9327 163.0279 103.5892 6.0666E-102 16564.4091 17211.4563 16677.5860 17098.27946
Odometer -0.05758 -0.06643 -0.04874 -0.063335537 -0.05183295
Explanation / Answer
Solution
Let x = odometer reading and y = used car price.
The regression equation is: y = + x.
Least square estimates: cap and cap
Given cap = 16887.9327 (intercept) and cap = - 0.05758 (odometer)
Part (1) Value of R2 = 0.793745372 = 0.6300 (rounded to 4 decimal places) ANSWER
Part (2) Standard error of the estimate (cap) = 0.004455 ANSWER
Details of computations:
100(1 - )% Confidence Interval (CI) for = cap ± {SE(b) x tn – 2,/2}, where n = number of observations and
tn – 2,/2 = upper (/2)% point of t-distribution with degrees of freedom = n – 2.
Given 95% CI for = (- 0.06643, - 0.04874), n = 100
t98, 0.025 = 1.9845 [using Excel Function]
So, - 0.04874 – (cap) = {SE(cap) x 1.9845
i.e., - 0.04874 – (- 0.05758) = {SE(cap) x 1.9845
Or, SE(cap) = 0.00884/1.9845 = 0.004455
Part (3)Test statistic for testing slope is non-zero: t = (cap - 0)/SE(cap) which is as tn – 2
Value of t = - 0.05758/0.004455 = - 12.9249 ANSWER
Part (4) p-value of t
Since t ~ t98, p-value = P(t98 > |t-value|) = P(t98 > | - 12.9249| ) = 6.76E-23 ANSWER [using Excel Function]
Part (5) Conclusion at 5% level of significance
Since p-value is much less than 0.05, there is enough evidence to conclude that slope is non-zero
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