69k views

### Minimum sample size for unpaired t-test

Is there a "rule" to determine the minimum sample size required for a t-test to be valid? For example, a comparison needs to be performed between the means of 2 populations. There are 7 data points ...
6k views

### Can you do statistics with 4 data points?

I was just involved in a Q/A were a poor guy was requested to run a statistical test to prove that algorithm A is better than two other algorithms. However, he has only 4 data points. Does it really ...
3k views

### Student's t vs Mann-Whitney U for small equal samples

I have 2 groups of data to compare using a t-test, both of sample size n=5. Checking to see if the normality assumption of the test holds is difficult since the sample sizes are too small. I have ...
4k views

### How to compare two groups when one only has one data point? [duplicate]

I have two groups I want to compare, however, I only have one data point in the first group compared to 450 data points in the second group. Here's the story. I have a patient that has a mutation in ...
833 views

### Two-sample t-test with one the samples having only 1 element?

In short Assume there is a normally distributed population, from which I take a sample with $N_1=5$ elements. Then I obtain a separate number $x$ from somewhere. I want to test whether the value $x$ ...
173 views

### Parametric test or nonparametric?

I have 2 groups of sample sizes 10 and 11 respectively. Can I apply a parametric or nonparametric test to find a significant difference in means between the groups?
2k views

### What is the correct way of comparing two very small groups (N = 3)?

I have 3 samples of water contamination (bacteria/L) from a lake which I want to compare to another, more "pristine" lake. So I have 6 values in total, 3 belonging to each lake: ...
1k views

### For a T-test, what would happen if one of my samples was made up of only one observation? [duplicate]

I must be missing something, or under-thinking what goes on with a basic T Test, but I was under the impression that if I do a T-test, and one of my samples was made up of only one observation, the ...
133 views

### How to check if removing a sample makes a difference in mean and stdev values?

I'd like to ask if someone could help me with the following problem: we have measured the same sample 5 times and we would like to check if there are significant differences in mean and stdev values ...
9k views

### t-test using a sample less than 30 [duplicate]

When I do the two tailed t-test using a sample less than 30, can I use this result? This is because I do also still see the t-test table which has degrees of freedom far less than 30. How further ...
359 views

### does ANOVA have to work on groups with replicates? [duplicate]

I want to test if the means of different groups (tissue types) are different using one-way ANOVA. Most of the groups have replicates but there is one group that only has one sample. Like this: heart, ...
59 views

### How do I determine the likelihood of a single measurement coming from a known distribution? [duplicate]

I have a set of 2000 numbers that form an approximately normal distribution, with a mean of about 0.24, and an SD of 0.06. These form an estimate of the population. I now have a single sample ...