Z test testing the difference between two means

Z test  is any statistical test for which the distribution of the test statistic under the null hypothesis can be approximated by a normal distribution.

Hypothesis Test:

formula:

where X₁ and   X₂ are the means of the two samples, ∆ is the hypothesized difference between the population means (0 if testing for equal means), σ₁and σ2 are the standard deviations of the two populations, N₁and N₂ are the sizes  of the two samples 


by: Oscar Pepin Marfil