Difference between revisions of "Durbin-Watson"
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| Line 28: | Line 28: | ||
* if D < lower bound, positive correlation exists. | * if D < lower bound, positive correlation exists. | ||
* if D is in between the two bounds, the test is inconclusive. | * if D is in between the two bounds, the test is inconclusive. | ||
| + | |||
| + | ==Example== | ||
| + | {| class="wikitable" | ||
| + | |+Spreadsheet | ||
| + | |- | ||
| + | ! !! A !! B | ||
| + | |- | ||
| + | ! 1 | ||
| + | | 3 || 7 || 5 || 65 | ||
| + | |- | ||
| + | ! 2 | ||
| + | | 4 || 3 || 7 || 38 | ||
| + | |- | ||
| + | ! 3 | ||
| + | | 5 || 5 || 8 || 51 | ||
| + | |- | ||
| + | ! 4 | ||
| + | | 6 || 8 || 1 || 38 | ||
| + | |- | ||
| + | !5 | ||
| + | | 7 || 9 || 3 || 55 | ||
| + | |- | ||
| + | !6 | ||
| + | | 8 || 5 || 4 || 43 | ||
| + | |- | ||
| + | !7 | ||
| + | | 2 || 4 || 0 || 25 | ||
| + | |- | ||
| + | !8 | ||
| + | | 3 || 2 || 6 || 33 | ||
| + | |- | ||
| + | !9 | ||
| + | | 8 || 8 || 7 || 71 | ||
| + | |- | ||
| + | !10 | ||
| + | | 9 || 6 || 4 || 51 | ||
| + | |- | ||
| + | !11 | ||
| + | | 2 || 9 || 2 || 49 | ||
| + | |} | ||
Revision as of 07:02, 3 May 2017
DURBINWATSONTEST(DataRange,ConfidenceLevel,NewTableFlag))
- Failed to parse (MathML with SVG or PNG fallback (recommended for modern browsers and accessibility tools): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle DataRange} is the array of x and y values.
- Failed to parse (MathML with SVG or PNG fallback (recommended for modern browsers and accessibility tools): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle ConfidenceLevel} is the value of alpha from 0 to 1.
- Failed to parse (MathML with SVG or PNG fallback (recommended for modern browsers and accessibility tools): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle NewTableFlag} is either TRUE or FALSE. TRUE for getting results in a new cube. FALSE will display results in the same cube
Description
- This function gives the test statistic of the Durbin-Watson test.
- The test is used to detect the presence of autocorrelation in the residuals.
- Autocorrelation means that adjacent observations are correlated.
- If they are correlated, then least-squares regression underestimates the standard error of the coefficients.
Assumptions
The error terms are independent of each other.
- The Durbin-Watson test uses the following statistic:
Failed to parse (MathML with SVG or PNG fallback (recommended for modern browsers and accessibility tools): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle d=\frac{\sum_{i=2}^n (e_i-e_{i-1})^2)}{\sum_{i=1}^n (e_i)^2}}
- where the Failed to parse (MathML with SVG or PNG fallback (recommended for modern browsers and accessibility tools): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle e_i = y_i-\bar{y_i}} are the residuals.
- n is the number of elements in the sample.
- k is the number of independent variables.
d takes the values between 0 and 4. * d = 2 means there is no autocorrelation. * A value substantially below 2 means that the data is positively autocorrelated. * A value of d substantially above 2 means that the data is negatively autocorrelated.
Result
* if D > upper bound, no correlation exists. * if D < lower bound, positive correlation exists. * if D is in between the two bounds, the test is inconclusive.
Example
| A | B | |||
|---|---|---|---|---|
| 1 | 3 | 7 | 5 | 65 |
| 2 | 4 | 3 | 7 | 38 |
| 3 | 5 | 5 | 8 | 51 |
| 4 | 6 | 8 | 1 | 38 |
| 5 | 7 | 9 | 3 | 55 |
| 6 | 8 | 5 | 4 | 43 |
| 7 | 2 | 4 | 0 | 25 |
| 8 | 3 | 2 | 6 | 33 |
| 9 | 8 | 8 | 7 | 71 |
| 10 | 9 | 6 | 4 | 51 |
| 11 | 2 | 9 | 2 | 49 |