As part of a lesson on statistical inference an enterprising statistics teacher gave his class of 15 students an "Ice Cream Taste Test". The results showed that 9 students preferred the chocolate ice cream, while 6 students preferred the vanilla ice cream. Use Table 5 to determine the following confidence intervals.
a) Estimate the true proportion of those preferring chocolate ice cream using a 90% confidence interval.
b) Estimate the true proportion of those preferring chocolate ice cream using a 95% confidence interval.