To assess improvement in the Chinese Centers for Disease Control and Prevention (CDCs) system between 2002 and 2012, two national cross-sectional surveys of 489 county-level CDCs were carried in 2002 and 2012. Each survey assessed the completeness of public health services (PHSs) for 7 different indexes of health care and overall. The completeness of PHSs ranged from 0% (not provided at all) to 100% (fully provided). In 2002 the mean (SD) for overall completeness of PHSs was 47.4% (24.3%) and in 2012 the mean (SD) for overall completeness of PHSs was 76.6% (4.4%)

a. Compute two 95% confidence intervals for the mean overall completeness of PHSs in 2002 and 2012.
b. What is the interpretation of the 95% confidence intervals you computed in part A?
c. Is there evidence from the surveys that the overall completeness of public health services (PHSs) improved between 2002 and 2012? Explain why.