Answer: (7.27%, 7.55%)
Step-by-step explanation:
As per given , we have
Sample size : n= 392
Sample mean :
Critical two-tailed z-value for 95% confidence =
Required confidence interval would be :
Hence, the required 95% confidence interval for the mean percentage share of billing volume from network television for the population of all U.S. advertising agencies : (7.27%, 7.55%)