A survey was designed and conducted to rate the services of two competing companies that are providing cell phone coverage in a metropolitan area. Two groups were selected in the same month to compare their survey responses and the details are below:

Company 1 :

n1: 175 xbar1= 3.85 s1=0.64

Company 2:

n2= 415 xbar2= 4.1 s2= 0.54

Survey results were reported from 1-5

Build the confidence interval for the mean difference between the two population.