Answer and Step-by-step explanation:
To calculate a confidence interval for a proportion:
1) Determine the proportion
p = 0.616
2) A 90% confidence interval has z-score that is 1.645.
3) Calculate margin of error
where
n is the sample size
So
ME = 0.02175
Then the interval is given by
p ± z(ME)
0.62 ± 1.645(0.02175)
0.62 ± 0.035
The interval will be
0.585 < p < 0.655
What this means is that we are 90% confident that the true proportion of Katy Perry's Twitter female followers is between 0.585 and 0.655.