In: Statistics and Probability
| Dep.= | Mileage | Indep.= | Octane | |||
| SUMMARY OUTPUT | ||||||
| Regression Statistics | ||||||
| Multiple R | ||||||
| R Square | ||||||
| Adjusted R Square | ||||||
| Standard Error | ||||||
| Observations | 7.0000 | |||||
| ANOVA | ||||||
| Significance | ||||||
| df | SS | MS | F | F | ||
| Regression | 9.1970 | |||||
| Residual | ||||||
| Total | 169.4286 | |||||
| Standard | ||||||
| Coefficients | Error | t Stat | P-value | Lower 95% | Upper 95% | |
| Intercept | -115.6768 | |||||
| Octane | 1.5305 | |||||
| SE | CI | CI | PI | PI | ||
| Predicted | Predicted | Lower | Upper | Lower | Upper | |
| x0 | Value | Value | 95% | 95% | 95% | 95% |
| 89.0000 | 1.4274 | |||||
| 87.0000 | 2.0544 |
Is there a relationship between a car's gas MILEAGE (in miles/gallon) and the OCTANE rating of its gas? Use the excel output above to answer the following question.
What is the 95% confidence interval for the mean gas mileage of cars that use 89 octane gas (without units)?
| a. |
(17.6615, 23.4139) |
|
| b. |
None of the answers is correct |
|
| c. |
(18.4309, 22.6445) |
|
| d. |
(16.8679, 24.2075) |
|
| e. |
(17.0449, 24.0305) |
X Value= 89
Confidence Level= 95%
Sample Size , n= 7
Degrees of Freedom,df=n-2 = 5
critical t Value=tα/2 = 2.571 [excel
function: =t.inv.2t(α/2,df) ]
Predicted Y at X= 89 is
Ŷ = -115.6768 +
1.5305 *89= 20.538
standard error, S(ŷ)= 1.427
margin of error,E=t*Std error=t* S(ŷ) =
2.5706 * 1.427 =
3.6692
Confidence Lower Limit=Ŷ +E = 20.538
- 3.669 = 16.8685
Confidence Upper Limit=Ŷ +E = 20.538
+ 3.669 = 24.2069
answer:
|
(16.8679, 24.2075) |