A Phoenix Wealth Management or Harris Interactive survey of 1500 individuals with the net worth of $1 million or more provided a variety of statistics on wealthy people (BusinessWeek, September 22, 2003). The previous 3 year period had been bad for the stock market, which motivated some of the questions asked.
a. The survey reported that the 53% of the respondents lost 25% or more of their portfolio value over the past three years. Make 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 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 previous year. Make a 95% confidence interval for the proportion who gave $25,000 or more to charity.