Biology Forums - Study Force

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The t test above is a parametric test. What are the circumstances where you will not a be able to use t test and instead use a non parametric test? What, given the specific t-test employed above, would this non parametric test entail?

One-sample t-tests can only be used when the data is normally distributed; this is why it is called a parametric test. Non-parametric tests are used when your data isn't normal. Therefore the key is to figure out if you have normally distributed data.

Here we see the Levene's test applied. Levene's test is used to assess aariance homogeneity, which is a precondition for parametric tests such as the t-test and ANOVA. The test can be used with two or more samples. With two samples, it provides the test of variance homogeneity for the t-test. If the significance from this test is less than 0.05, then variances are significantly different and parametric tests cannot be used (and a non-parametric test will probably have to be used). Notice in our data, we have an F value of 0.037. This is less than 0.05. A value less than .05 indicates a violation of the assumption. If a violation occurs, it is likely that conducting the non-parametric equivalent of the analysis is more appropriate.

Thank you very much sir/mam!!

Post Merge: A year ago

Another question sir/mam, from the gathered result, should the null hypothesis be rejected or be accepted?

I believe you reject the null hypothesis in favor of the alternative hypothesis because 0.037 < 0.05. This suggests the groups are in fact different.

Sir/mam, one last question, based on t test's result, what conclusion can be made sir/mam?

The groups are different. So the treatment used on group 1 had results that were significantly different than the treatment used in group 2.

Thank you very much sir!