Hello Mr Shakil

In reference to your query, an independent t-test is performed for comparing the means between two unrelated groups on the same continuous, dependent variable. This also means that the two groups have to be unrelated to each other in terms of participant characteristics. This may also be considered as an issue under study design but important as far as independent t-tests are concerned. 

I may also want to direct your attention to the link: https://statistics.laerd.com/spss-tutorials/independent-t-test-using-spss-statistics.php

Specific assumptions regarding independent t-test are outlined in this link which am sure will help you understand better. 

The design of the study in particular is more useful for sample size calculations than the statistical test. 

Hope this clarifies your concerns satisfactorily. 

Hello Shakil,

I could not find any guidance on minimum sample size regarding independent sample t test. Is it good news? Not sure. To compare means you need at least 2 observations per group. However with small sample size your research may be hugely underpowered. Hence any attempt to generalize your findings could be questioned. 

So it does depend what you would like to do with your results, I think that is the key issue.

Regards, Witold

Shakil -

I worked in that area many years ago, and as I recall, and it seems logical, it is most efficient if the two samples are the same size.  As one becomes substantially larger than the other, there is little to gain by adding to that sample.

Overall, various hypothesis tests are often misused anyway.

 https://www.researchgate.net/publication/262971440_Practical_Interpretation_of_Hypothesis_Tests_-_letter_to_the_editor_-_TAS

Best wishes - Jim

Article Practical Interpretation of Hypothesis Tests - letter to the...

Hi Shakil,

Firstly, you should use this test to compare two small sets of quantitative data when samples are collected independently of one another. When one randomly takes replicate measurements from a population he/she is collecting an independent sample, or use of a paired t test, to which some statistics programs unfortunately default, requires nonrandom sampling.

Criteria that you should adopt when working with independent t test:

- Only if there is a direct relationship between each specific data point in the first set and one and only one specific data point in the second set, such as measurements on the same subject 'before and after,' then the paired t test MAY be appropriate.

- If samples are collected from two different populations or from randomly selected individuals from the same population at different times, use the test for independent samples (unpaired).

- If one sample can have a different number of data points from the other, then the paired t test cannot apply.

So, I agree with Mr. Knaub, it is most efficient if the two samples are the same size.

Best regards,

Hello Mr Shakil,

We use it to test the hypotheses that determine the significance of difference appear softer analyzed.

Best regards

Of course that depends on the sample size.

What is the difference between the death rate and fatality rate?

 Mortality rate is the number of dead compared to the number of population and the rate of fatality numbers of deaths from a disease compared to the number of the register of a particular disease.

.It is indicated for testing the significance of the difference between two proportions