The IRS reported that 62% of individual tax returns were filed electronically in 2008. A random sample of 225 tax returns from 2010 was selected. From this sample, 163 were filed electronically.
a) Construct a 95% confidence interval to estimate the actual proportion of taxpayers who filed electronically in 2010.
b) What is the margin of error for this sample?
c) Is there any evidence that this proportion has changed since 2008 based on this sample?