Common Hypotheses
H0 : µ1 - µ2 = 0 Ha : µ1 - µ2 ≠ 0
H0 : µ1 - µ2 = 0 Ha : µ1 - µ2 < 0
H0 : µ1 - µ2 = 0 Ha : µ1 - µ2 > 0
Assumptions
Two independent random samples or two groups in a randomized experiment.
Sampling with replacement (or sample size < 10% N)
If the observed distribution is skewed in either of the sample, then that sample size n should be greater than 30.
If the sample size is less than 30, the distribution of the sample data should be free from strong skewness and outliers.
Sampling Distribution
Student's t (if σ unknown)
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