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How do you find the variance between groups?
Subtract each of the scores from the mean of the entire sample. Square each of those deviations. Add those up for each group, then add the two groups together. This is just like computing the variance.
What is within group variance and between group variance?
ANOVA stands for ‘Analysis of variance’ as it uses the ratio of between group variation to within group variation, when deciding if there is a statistically significant difference between the groups. Within group variation measures how much the individuals vary from their group mean.
How is a t test used to calculate variance?
A t-test is performed, which can be visually explained by plotting the protein concentration on the X-axis and the frequency along the Y-axis of the two proteins on the same graph (Figures 1 – 4). Proteins 1 & 2 have the same difference in protein concentration means but different group variances.
Can a t test be used for more than two groups?
A t-test should not be used to measure differences among more than two groups, because the error structure for a t-test will underestimate the actual error when many groups are being compared. If you want to compare the means of several groups at once, it’s best to use another statistical test such as ANOVA or a post-hoc test.
What are the two types of t test?
There are two types of t-tests: 1. Independent samples t-test. This is used when we wish to compare the difference between the means of two groups and the groups are completely independent of each other.
When to use a paired or two sample t test?
If you are studying one group, use a paired t-test to compare the group mean over time or after an intervention, or use a one-sample t-test to compare the group mean to a standard value. If you are studying two groups, use a two-sample t-test. If you want to know only whether a difference exists, use a two-tailed test.