Question 1187177
sample size = 10000
mean proportion = 4500/10000 = .45
1 - mean proportion = 1 - .45 = .55
standard error of mean proportion = sqrt(.45 * .55 / 1000) = .0049749372.


two tailed critical z-score for 90% confidence interval = plus or minus 1.645.


low sample mean proportion = -1.645 * .0049749372 + .45 = .4418162283.
high sample mean proportion = 1.645 * .0049749372 + .45 = .4581837717.


multiply the proportions by 10,000 and you'll get.


mean = .45 * 10000 = 4500
low sample mean = .4418162283 * 10000 = 4418.162283.
high sample mean = .4581837717 * 10000 = 4581.837717.


at 90% confidence interval, the size of the population of the SADC region that buys a certain company's product will be somewhere between 4418.162283 and 4581.837717.


that's what i get.