Z Alpha/2 (za/2): What is it, How to Find it.

The term "z/2" is used in statistics to refer to the critical value from the table.

The exact value of 0.05 doesn't show up in the table, but it would be between the two values.The critical values on the outside of the table are -1.64 and -1.65.

The critical value is -1.645 if we split the difference.The absolute value is typically taken when we use Z/2.Thus, Z.01/2 is 1.645

The calculator will return the value of 1.645 if we enter 0.1 as the significance level and the test uses a 90% confidence level.