Using the z-distribution, it is found that the z-value is of z = -2.29.
For a confidence level of [tex]\alpha[/tex], it is Z with a p-value of [tex]\frac{1 + \alpha}{2}[/tex].
We have a 97.8% confidence level, hence[tex]\alpha = 0.978[/tex], z is the value of Z that has a p-value of [tex]\frac{1+0.978}{2} = 0.989[/tex], so the critical value is z = -2.29.
More can be learned about the z-distribution at https://brainly.com/question/25890103
