To calculate the z-statistic, we must first calculate the standard error.
Standard error is standard deviation divided by the square root of the population. In this case, it is equal to 1.81.
The z-score is defined the distance from the sample to the population mean in units of standard error.
z = (26 – 20)/1.81 = 3.31
at this z-score = 0.0005 which is less than 5%
the answer is C. the z- statistic is 3.32, so the null hypothesis should be rejected.
