A Phoenix Wealth Management or Harris Interactive survey of the 1500 individuals with net worth of $1 million or more provided the variety of statistics on wealthy people (Business Week, September 22, 2003). The previous three-year time had been bad for the stock market, which motivated some of the questions asked.
a. The survey reported that 53% of respondents lost 25% or more of their collection value over the past three years. Build up a 95% confidence interval for the proportion of the wealthy people who lost 25% or more of their portfolio value over the past three years.
b. The survey reported that the 31% of the respondents feel they have to save more for the retirement to make up for what they lost. Make a 95% confidence interval for the population proportion.
c. Five percent of respondents gave $25,000 or more to charity over the preceding year. Make a 95% confidence interval for proportion who gave $25,000 or more to charity.