#+TITLE: Rapport package team
#+AUTHOR: Brown-Forsyth test
#+DATE: 2011-04-26 20:25 CET
** Description
This template will run a Brown-Forsyth test to check the equality of
variances among groups.
*** Introduction
The Brown-Forsyth test is used for checking the equality of the
variances among the groups of one variable, in other words it tests the
homogeneity of the variances. Equality of group variances is an
assumption of the one-way ANOVA test.
The base of the test is really similar to the Levene's test, but the
Brown-Forsyth test uses the deviations from the group medians instead of
the mean (what the Levene's does), thus the Brown-Forsyth test is called
more robust.
This test has the advantage over the other tests, which are also being
used to check the homogeneity (F-test and Bartlett's test), that it does
not have a normality assumption, so the variable we investigate do not
have to follow a normal distribution.
**** References
- Brown, M.~B. and Forsyth, A.~B. (1974). Robust tests for equality of
variances. /Journal of the American Statistical Association/,
69:364-367.
*** Result
| Method | Statistic | p-value |
|----------------------+-------------+-----------|
| hov: Brown-Forsyth | 0.3847 | 0.5353 |
According to the /Brown-Forsyth test/, the variances of the /Age/ across
the groups of /Gender/ does not differs significantly.
We can conclude that, because the p-value is higher than 0.05
**** References
- Heiberger, Richard M. and Holland, Burt (2004b). /Statistical
Analysis and Data Display: An Intermediate Course with Examples in
S-Plus, R, and SAS/.
** Description
This template will run a Brown-Forsyth test to check the equality of
variances among groups.
*** Introduction
The Brown-Forsyth test is used for checking the equality of the
variances among the groups of one variable, in other words it tests the
homogeneity of the variances. Equality of group variances is an
assumption of the one-way ANOVA test.
The base of the test is really similar to the Levene's test, but the
Brown-Forsyth test uses the deviations from the group medians instead of
the mean (what the Levene's does), thus the Brown-Forsyth test is called
more robust.
This test has the advantage over the other tests, which are also being
used to check the homogeneity (F-test and Bartlett's test), that it does
not have a normality assumption, so the variable we investigate do not
have to follow a normal distribution.
**** References
- Brown, M.~B. and Forsyth, A.~B. (1974). Robust tests for equality of
variances. /Journal of the American Statistical Association/,
69:364-367.
*** Result
| Method | Statistic | p-value |
|----------------------+-------------+-----------|
| hov: Brown-Forsyth | 4.681 | 0.03087 |
According to the /Brown-Forsyth test/, the variances of the /Internet
usage for educational purposes (hours per day)/ across the groups of
/Gender/ significantly differs.
We can conclude that, because the p-value is smaller than 0.05
**** References
- Heiberger, Richard M. and Holland, Burt (2004b). /Statistical
Analysis and Data Display: An Intermediate Course with Examples in
S-Plus, R, and SAS/.
** Description
This template will run a Brown-Forsyth test to check the equality of
variances among groups.
*** Introduction
The Brown-Forsyth test is used for checking the equality of the
variances among the groups of one variable, in other words it tests the
homogeneity of the variances. Equality of group variances is an
assumption of the one-way ANOVA test.
The base of the test is really similar to the Levene's test, but the
Brown-Forsyth test uses the deviations from the group medians instead of
the mean (what the Levene's does), thus the Brown-Forsyth test is called
more robust.
This test has the advantage over the other tests, which are also being
used to check the homogeneity (F-test and Bartlett's test), that it does
not have a normality assumption, so the variable we investigate do not
have to follow a normal distribution.
**** References
- Brown, M.~B. and Forsyth, A.~B. (1974). Robust tests for equality of
variances. /Journal of the American Statistical Association/,
69:364-367.
*** Result
| Method | Statistic | p-value |
|----------------------+-------------+-------------|
| hov: Brown-Forsyth | 15.89 | 2.131e-12 |
According to the /Brown-Forsyth test/, the variances of the /Internet
usage for educational purposes (hours per day)/ across the groups of
/How often does your profession require Internet access?/ significantly
differs.
We can conclude that, because the p-value is smaller than 0.05
**** References
- Heiberger, Richard M. and Holland, Burt (2004b). /Statistical
Analysis and Data Display: An Intermediate Course with Examples in
S-Plus, R, and SAS/.
--------------
This report was generated with [[http://www.r-project.org/][R]] (3.0.1)
and [[http://rapport-package.info/][rapport]] (0.51) in /0.762/ sec on
x86\_64-unknown-linux-gnu platform.
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