Consider the following data drawn independently from normally distributed populations: (You may find it useful to reference the appropriote toble: ztable or t table) x1=18.1s12=8.2n1=13x2=17.0s22=8.7n2=13 a. Construct the 99% confidence interval for the difference between the population means. Assume the population variances are unknown but equal. (Round final answers to 2 decimal places.) b. Specify the competing hypotheses in order to determine whether or not the population means differ. H:12=;HA:12=H:12;HA:12<12><12>