Answer:
(-0.1018, 0.0018)
Step-by-step explanation:
Given that a bank wants to get new customers for their credit card. They try two different approaches in their marketing campaign. The first promises a "cash back" reward; the second promises low interest rates. A sample of 500 people was mailed the first brochure; of these, 100 get the credit card. A separate sample of 500 people was mailed the second brochure; 125 get the credit card.
i.e. p1 = [tex]100/500 = 0.2[/tex]
p2 = [tex]125/500 = 0.25[/tex]
p difference = [tex]-0.05[/tex]
Combined p = [tex]\frac{100+125}{500+500} \\=0.225[/tex]
1-p = 0.775
Std error for difference = [tex]\sqrt{0.225*0.775)(\frac{1}{500} +\frac{1}{500}} )\\=0.02641[/tex]
Margin of error for 95%
=1.96 * std error = 0.0518
Confidence interval for differnce =
[tex](-0.05-0.0518, -0.05+0.0518)\\= (-0.1018, 0.0018)[/tex]