Refer to the previous exercise. The report from the Pew Research Center also provided survey results for different age groups:
• Among those aged 18 to 29, 89% of 395 used social networking sites.
• Among those aged 30 to 49, 78% of 542 used social networking sites.
• Among those aged 50 to 64, 60% of 553 used social networking sites.
• Among those aged 65 and older, 43% of 356 used social networking sites.

a. For each age group, determine and interpret a 95% confidence interval for the relevant parameter.

b. How do the margins of error for these age-specific confidence intervals compare to the margin of error based on the entire sample (larger, smaller, or the same)? Explain why this makes sense.