Question

How to Find a Critical Z Value 

LEARNING OBJECTIVE: Calculate a critical z-score for a left-tailed, right-tailed, or two-tailed test. 

Select the correct statement. 

 a.) The critical z-score for a left-tailed test at a 12% significance level is -0.45. 

 b.) The critical z-score for a right-tailed test at a 9% significance level is 1.34. 

 c.) The critical z-score for a two-sided test at a 4% significance level is 1.75. 

 d.) The critical z-score for a two-sided test at a 20% significance level is 0.85.

Answer 1

The statement b

a. This statement is false because

P( z < -0.45 ) = 0.3264

b. This statement is correct because,

P( z > 1.34 ) = 1 - P(z < 1.34) = 1 - 0.9099 = 0.09

c. This statement is false because

If 1.75 is critical z score for two sided test at a 4% level of significance then probability less than -1.75 is 0.02 and probability greater than 1.75 is 0.02.

But,

P(z<-1.75)=0.04

d. This statement is false because

If 0.85 is critical z score for two sided test at a 20% level of significance then probability less than -0.85 is 0.10 and probability greater than 0.85 is 0.10.

But,

P(z<-0.85)=0.20

P(-1.75 < z < 1.75) = P( z<1.75 ) - P(z < -1.75 ) = 0.9599 - 0.04 =