1. A health survey done on a random sample of 80 working adults found that 12 of them have hypertension. Construct a 93% confidence interval for the proportion of working adults who had hypertension. Interpret your results.
2. The masses of grade A oranges sold at a hypermarket are normally distributed with mean and variance 100. If the manager of the hypermarket wishes to estimate the mean mass with a maximum allowable error of 2.5 using 98% confidence level, find the minimum number of oranges needs to be selected as sample.