The critical value for assessing the difference between two proportions at the 0.05 level, or .025 proportion in one tail, is 1.96 for an experiment that includes samples where estimates must be made for the mean and standard deviation, therefore this is not a Z table problem (please see your notes). Sometimes Always Never

The critical value for assessing the difference between two proportions at the 0.05 level, or .025 proportion in one tail, is 1.96 for an experiment that includes samples where estimates must be made for the mean and standard deviation, therefore this is not a Z table problem (please see your notes). Sometimes Always ONever