If you have a population of 500,000 people how many to be sample to give a representative profile with only a 5% point margin of error ?
I'm not sure what you mean by "representative profile." For an estimate of a mean, ± 2 standard error give approximately a 95% confidence interval, leaving a 5% margin of error.
Standard error = standard deviation/sqrt of N, where N = number in the sample.
I hope this helps. Thanks for asking.