Thank you so much, that's the answer I've got.

Just a quick question regarding the Z_crit value. I calculated Z_crit = Z_0.05 = -1.645. I got this value using the normal statistical tables:

From the normal tables, Z_0.05 is not stated.

Calculate Z_0.05 by using values for Z_0.0495 and Z_0.0505 and take average of the two.

Z_crit = Z_0.05 = [(-1.64) + (-1.65)] / 2 = -1.645

Therefore, we will reject H₀ if Z_obs > -1.645.

Why is Z_crit always positive for a right tail test? And is Z_crit always negative for a left tail test then?