Two competing toothpaste brands both claim to produce the best toothpaste for whitening . A dentist randomly samples 48 patients that use Brand A Group 1 and finds 30 of them are satisfied with the whitening results of the toothpaste . She then randomly samples 45 patients that use Brand B Group 2 and finds 33 of them are satisfied with the whitening results of the toothpaste . Construct a 99 % confidence interval for the difference in proportions and use it to decide if there is a significant difference in the satisfaction level of patients .