Python t-test unequal sample size
Renesh Bedre 9 minute read Show Student’s t-test
Types of t-testOne Sample t-test
Assumptions
Hypotheses
Learn more about hypothesis testing and interpretation FormulaOne Sample t-test formula, Calculate one sample t-test in Python
Note: If you have your own dataset, you should import it as pandas dataframe. Learn how to import data using pandas Perform one sample t-test using SciPy,
Perform one sample t-test using bioinfokit,
InterpretationThe p value obtained from the one sample t-test is not significant (p > 0.05), and therefore, we conclude that the average diameter of the balls in a random sample is equal to 5 cm. Check how to perform one sample t-test from scratch Check how to calculate p value by hand Two sample t-test (unpaired or independent t-test)The two-sample (unpaired or independent) t-test compares the means of two independent groups, determining whether they are equal or significantly different. In two sample t-test, usually, we compute the sample means from two groups and derives the conclusion for the population’s means (unknown means) from which two groups are drawn. For example, we have two different plant genotypes (genotype A and genotype B) and would like to compare if the yield of genotype A is significantly different from genotype B Hypotheses
Learn more about hypothesis testing and interpretation Assumptions
If the sample size small and does not follow the normal distribution, you should use non-parametric Mann-Whitney U test (Wilcoxon rank sum test) FormulaTwo sample (independent) t-test formula, If the variances are equal, the two sample t-test and Welch’s test (unequal variance t-test) perform equally (in terms of type I error rate) and have similar power. Calculate Two sample t-test in Python
Perform two sample t-test using SciPy,
Perform two sample t-test using bioinfokit,
InterpretationThe p value obtained from the t-test is significant (p < 0.05), and therefore, we conclude that the yield of genotype A is significantly different than genotype B. Check how to perform two sample t-test from scratch Check how to calculate p value by hand Paired t-test (dependent t-test)
Hypotheses
Learn more about hypothesis testing and interpretation Assumptions
FormulaPaired t-test formula, Perform Paired t-test,
InterpretationThe p value obtained from the t-test is significant (p < 0.05), and therefore, we conclude that the yield of plant variety A significantly increased by the application of fertilizer. Check how to perform paired sample t-test from scratch Note: If you have partially paired data, you can use an independent t-test by treating two dependent variables as two different samples or drop all unpaired observations for performing paired t-test. But, both ad hoc approaches are not appropriate as it does not follow the basic requirement and may lead to biased estimate of the variance and loss of information 6. Sample size recommendations for t-test
Check how to perform t-test from scratch Enhance your skills with courses on statistics
References
If you enhanced your knowledge and practical skills from this article, consider supporting me on This work is licensed under a Creative Commons Attribution 4.0 International License Can I use tYes, you can perform a t-test when the sample sizes are not equal. Equal sample sizes is not one of the assumptions made in a t-test. The real issues arise when the two samples do not have equal variances, which is one of the assumptions made in a t-test.
How do you do a Welch's tTo conduct a Welch's t-test, one needs to use the stats. ttest_ind() method while passing “False” in the “equal_var=” argument. The p-value is significant, therefore one can reject the null hypothesis in support of the alternative. Another piece of information you will need to report is the degrees of freedom (DoF).
What is ttest_ind () in Python?Calculates the T-test for the means of TWO INDEPENDENT samples of scores. This is a two-sided test for the null hypothesis that 2 independent samples have identical average (expected) values. This test assumes that the populations have identical variances.
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