what is a wilcoxon sign-ranked test (pair t non para)?
DESCRIPTION
Decision-Based Learning - What is a Wilcoxon Sign-Ranked Test (pair t non para)?TRANSCRIPT
Wilcoxon Signed-Ranked Test (Paired T)
The Wilcoxon test is the non-parametric analogue to the pair-wise (repeated measures) t-test.
The non-parametric analogue to the pair-wise (repeated measures) t-test is the Wilcoxon test.
You may remember that the pair-wise (repeated measures) t-test is used to determine the statistical significant difference between the same sample/observations or people on two separate occasions.
Here is a simplified data set that would use a paired sample t-test:
Students Pre Post
1 1 7
2 2 6
3 1 8
mean: 1.3 7.0
Students Pre Post
1 1 7
2 2 6
3 1 8
mean: 1.3 7.0
Three students
Students Pre Post
1 1 7
2 2 6
3 1 8
mean: 1.3 7.0
Pre-Quiz
Students Pre Post
1 1 7
2 2 6
3 1 8
mean: 1.3 7.0
Students Receive Instruction
Students Pre Post
1 1 7
2 2 6
3 1 8
mean: 1.3 7.0
Post-Quiz
Students Pre Post
1 1 7
2 2 6
3 1 8
mean: 1.3 7.0
The Mean of the
Pre-quiz
Students Pre Post
1 1 7
2 2 6
3 1 8
mean: 1.3 7.0
The Mean of the
Pre-quizis compared to
Students Pre Post
1 1 7
2 2 6
3 1 8
mean: 1.3 7.0
The Mean of the
Pre-quizis compared to
The Mean of the
Post-quiz
Students Pre Post
1 1 7
2 2 6
3 1 8
mean: 1.3 7.0
The Mean of the
Pre-quizis compared to
The Mean of the
Post-quiz
using a Paired-Sample t-test
It appears that the post-test scores are higher than the pre-test scores. But what is the likelihood of getting this result if we tested one thousand samples of 3.0?
It appears that the post-test scores are higher than the pre-test scores. But what is the likelihood of getting this result if we tested one thousand samples of 3.0?We use the paired-sample t-test to test the likelihood of this result occurring by chance.
It appears that the post-test scores are higher than the pre-test scores. But what is the likelihood of getting this result if we tested one thousand samples of 3.0?We use the paired-sample t-test to test the likelihood of this result occurring by chance.But the Paired-sample t-test can be used when certain assumptions are met:
It appears that the post-test scores are higher than the pre-test scores. But what is the likelihood of getting this result if we tested one thousand samples of 3.0?We use the paired-sample t-test to test the likelihood of this result occurring by chance.But the Paired-sample t-test can be used when certain assumptions are met:1. the data is interval/ratio
It appears that the post-test scores are higher than the pre-test scores. But what is the likelihood of getting this result if we tested one thousand samples of 3.0?We use the paired-sample t-test to test the likelihood of this result occurring by chance.But the Paired-sample t-test can be used when certain assumptions are met:1. the data is interval/ratio2. the data is normally distributed
The Wilcoxon test is appropriate to use when the underlying measurement is on an ordinal scale.
The Wilcoxon test is appropriate to use when the underlying measurement is on an ordinal scale.
3rd Place 15’2”
2nd
Place 16’1”
1st Place 16’3”
3rd Place 15’2”
2nd
Place 16’1”
1st Place 16’3”
The distance between 3rd and 2nd place (11”) is not the same interval as the distance between 2nd and 1st place
(1”)
The Wilcoxon test is appropriate to use when the underlying measurement is on an ordinal scale or the distribution of a dependent variable is highly skewed.
The Wilcoxon test is appropriate to use when the underlying measurement is on an ordinal scale or the distribution of a dependent variable is highly skewed.
The Wilcoxon test is appropriate to use when the underlying measurement is on an ordinal scale or the distribution of a dependent variable is highly skewed.
Like the Paired Sample t-test, the Wilcoxon test will compare whether there are significant differences between the distributions between time-one and time-two.
Time 1 for Distribution A Time 2 for Distribution A
0 0
A Paired Sample t-test would be used if the distributions were more normal and the data were interval or ratio.
A Paired Sample t-test would be used if the distributions were more normal and the data were interval or ratio.
Interval/Ratio scales • assume quantity of the attribute.• have equal intervals.
The Wilcoxon like all nonparametric tests
The Wilcoxon like all nonparametric tests 1. is not sensitive to outliers and therefore is more
appropriate to use when the data is skewed.
The Wilcoxon like all nonparametric tests 1. is not sensitive to outliers and therefore is more
appropriate to use when the data is skewed.2. (uses the Median instead of the Mean and is
therefore more appropriate to use when the data is rank order or ordinal.