An independent samples t-test examines if 2 populations have equal means on some variable.
Example: do Dutch women have the same mean salary as Dutch men?
This tutorial quickly walks you through the basics such as the assumptions, null hypothesis and effect size for this test.
A paired samples t-test examines if 2 variables have equal means in some population.
Example: were the mean salaries over 2018 and 2019 equal for all Dutch citizens?
This tutorial quickly walks you through the correct steps for running this test in SPSS.
A one-sample t-test examines if a population mean is likely to be x: some hypothesized value.
Example: do the pupils from my school have a mean IQ score of 100?
This tutorial quickly walks you through the basics for this test, including assumptions, formulas and effect size.
Z-scores are scores that have mean = 0 and standard deviation = 1.
All scores can be standardized into z-scores by subtracting the mean from each score and then dividing it by the standard deviation.
Such standardized scores may be easier to interpret than the original scores. Z-scores may or may not be normally distributed.