biostats tests

# biostats tests - Student's t-test Use Student's t-test when...

This preview shows pages 1–3. Sign up to view the full content.

Student's t-test Use Student's t-test when you have one attribute variable and one measurement variable, and you want to compare the mean values of the measurement variable. The attribute variable must have only two values, such as "male" and "female" or "treated" and "untreated." Example: In fall 2004, students in the 2 p.m. section of Biological Statistics had an average height of 66.6 inches, while the average height in the 5 p.m. section was 64.6 inches. Are the average heights of the two sections significantly different? One-way anova Analysis of variance (anova) is the most commonly used technique for comparing the means of groups of measurement data. In a one-way anova there is one measurement variable and one attribute variable. Multiple observations of the measurement variable are made for each value of the attribute variable. all anovas, assumes that the observations within each cell are normally distributed and have equal variances . Example : you could measure the amount of transcript of a particular gene for multiple samples taken from arm muscle, heart muscle, brain, liver, and lung. The transcript amount would be the measurement variable, and the tissue type (arm muscle, brain, etc.) would be the attribute variable. Kruskal-Wallis test and Mann-Whitney U test The Kruskal-Wallis test is used when there is one attribute variable and one measurement variable, and the measurement variable does not meet the normality assumption of ANOVA. It is the non-parametric analogue of a one-way ANOVA. A one-way ANOVA may yield inaccurate estimates of the P-value when the data are very far from normally distributed. The Kruskal-Wallis test does not make assumptions about normality. It is performed on ranked data, so the measurement observations are converted to their ranks in the overall data set: the smallest value gets a rank of 1, the next smallest gets a rank of 2, and so on. The Mann-Whitney U-test or the Wilcoxon test or the Wilcoxon rank-sum test is limited to attribute variables with only two values; it is the non-parametric analogue to Student's t-test.

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Two-way anova Use a two-way ANOVA when you have one measurement variable and two attribute
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### Page1 / 4

biostats tests - Student's t-test Use Student's t-test when...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online