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Wrong wording in t-test

When one wants to run independent samples T-test, there are three possible tests:
1. Student, when the distribution is normal and the two samples have equal variances
2. Welch, when the distribution is normal and the two samples don't have equal variances
3. Mann-Whitney U test, when the distribution is not normal

When one wants to run paired samples T-test, there are two possible tests:
1. Student, when the distribution is normal
2. Wilcoxon signed rank, when the distribution is not normal

When one wants to run one sample T-test, there are two possible tests:
1. Student, when the distribution is normal
2. "Mann-Whitney U test", when the distribution is not normal

i)However, this test is not "Mann-Whitney U test", but "one sample Wilcoxon signed rank test". U test is only for two independent samples. Check this website: https://onlinecourses.science.psu.edu/stat414/node/319
I inserted in JASP exactly the same numbers, I selected one-sample T Test, "Mann-Whitney U" test, as you have named it, and test value "3.7". JASP calculated a p-value=0.232, the same with the website. This means that JASP performs the same test as described in the website, but you have named the test incorrectly.
This might be confusing, so please correct it.

ii) Wilcoxon test uses median in the hypothesis, and not mean. This should be corrected (see screenshot).

iii) When you use the word "hypothesis", you should specify that this is the alternative hypothesis.

Thanked by 1sebastiaan
Data.png 145.6K
u.png 282.9K

Comments

  • JohnnyBJohnnyB Posts: 14

    Hi Antonis,
    Thanks a lot for taking the time to point this out. You are absolutely correct - the wording in the analysis form will be updated in the next JASP release. The underlying analysis, thankfully, does use the correct version of the Wilcoxon test (sign rank), hence its similarity to the online tool you used.
    I will also update the hypothesis wording so that it is less confusing.
    Cheers,
    Johnny

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