According to market research by Brittain Associates, published in an issue of American Demographics, the income distribution of adult Internet users closely mirrors that of credit card applicants. That is exactly what many major credit card issuers want to hear because they hope to replace direct mail marketing with more efficient Web-based marketing. Following is an income distribution for credit card applicants.
Income ($1000) Percentage
Under 30 ............28
30–under 50 ............33
50–under 70 ............21
70 or more ............18
A random sample of 109 adult Internet users yielded the following income distribution.
Income ($1000) Frequency
Under 30 .............25
30–under 50 ............29
50–under 70 ............26
70 or more ..............29
a. Decide, at the 5% significance level, whether the data do not support the claim by Brittain Associates.
b. Repeat part (a) at the 10% significance level.