Step 1 :Given the standardized test statistic $z=1.988$
Step 2 :We are asked to determine whether we should reject or fail to reject the null hypothesis
Step 3 :The null hypothesis is typically rejected if the absolute value of the z-score is greater than 1.96 (for a confidence level of 95%)
Step 4 :This is because a z-score of 1.96 or higher (or -1.96 or lower) indicates that the observed data is very unlikely under the null hypothesis (less than 5% chance)
Step 5 :Therefore, if the z-score is greater than 1.96 or less than -1.96, we reject the null hypothesis
Step 6 :In this case, the z-score is 1.988, which is greater than 1.96
Step 7 :\(\boxed{\text{Therefore, we should reject the null hypothesis}}\)