333k views

### Is there a minimum sample size required for the t-test to be valid?

I'm currently working on a quasi-experimental research paper. I only have a sample size of 15 due to low population within the chosen area and that only 15 fit my criteria. Is 15 the minimum sample ...
8k views

### What can we say about population mean from a sample size of 1?

I am wondering what we can say, if anything, about the population mean, $\mu$ when all I have is one measurement, $y_1$ (sample size of 1). Obviously, we'd love to have more measurements, but we can'...
2k views

### What to say to a client that thinks confidence intervals are too wide to be useful?

Suppose I am a consultant and I want to explain to my client the usefulness of confidence interval. The client says to me that my intervals are too wide to be useful and he would prefer to use ones ...
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 ...
8k views

### When data has a gaussian distribution, how many samples will characterise it?

Gaussian data distributed in a single dimension requires two parameters to characterise it (mean, variance), and rumour has it that around 30 randomly-selected samples is usually sufficient to ...
4k views

### Is it ever appropriate to fit a regression on 3 points?

Lets assume we only have 2 variables, x and y, and our model (in R code) is lm(y~x). Given ...
823 views

### Which statistical test to use when there's no data of SD but just know the mean?

In our lab, we work with the retina which yields very little sample. Although we have a reasonable sample size of six animals in each group, I don't understand which test to be used to test for ...
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 ...
6k views

### Minimum sample size for t-test [duplicate]

Can you do a t-test or ANOVA between 2 or 3 groups respectively if one of those groups has a sample size of 2? Are the results interpretable in the same way as with larger sample sizes(n=4,5,6?). If ...
1k views

### sample size to get 99.6% confidence on a one-tailed test

If I have a normally distributed population of 3.5 million elements, and I want to sample enough of them to make a statement with 99.6% confidence on a 1-tailed test, what should my sample size be? ...