When NYSE, NASDAQ, and the British government bonds market were planning to change prices of shares and bonds from powers of 2, such as 1/2, 1/4, 1/8, 1/16, 1/32, to decimals (hence 1/32 = 0.03125), they decided to run a test.
If the test run of trading rooms using the new system revealed that 80% of the traders preferred the decimal system and the sample size was 200, give a 95% confidence interval for the percentage of all traders who will prefer the new system.