The standardized test statistic can be found using technology or the formula below, where x overbar 1, sigma 1, and n 1 are the sample mean, population standard deviation, and sample size of sample 1, respectively, and x overbar 2, sigma 2, and n 2 are the sample mean, population standard deviation, and sample size of sample 2, respectively. zequalsStartFraction left parenthesis x overbar 1 minus x overbar 2 right parenthesis minus left parenthesis mu 1 minus mu 2 right parenthesis Over sigma Subscript x overbar 1 minus x overbar 2 EndFraction , where sigma Subscript x overbar 1 minus x overbar 2equalsStartRoot StartFraction sigma Subscript 1 Superscript 2 Over n 1 EndFraction plus StartFraction sigma Subscript 2 Superscript 2 Over n 2 EndFraction EndRoot