Two sample t-test

what is a two sample t test used for?

comparing means between two groups of different, unrelated participants

what are other names for a two sample t test?

• independent samples

• between subjects

• unpaired or unrelated t test

What is the difference between student’s and welch’s t test?

student’s assume equal variances; welch’s does not

why is welch’s t test often recommended as the default?

it works well with equal variances and better controls Type I error when variances differ

why is the non-parametric alternative to a sample t-test?

The Mann-Whitney U test

what are the main two sample t test assumptions?

• continuous outcome

• independent observations

• approximately normal residuals within groups

• students also assumes equal variances

What does Levene’s test asses?

principles guiding judgements about right and wrong, including fairness, honesty and respect