In: Statistics and Probability
In a sample of 410 adults, 246 had children. Construct a 90%
confidence interval for the true population proportion of adults
with children.
Give your answers as decimals, to three places
_______ < p < _______
Solution :
Given that,
Point estimate = sample proportion = 
 = x / n = 246 / 410 = 0.600
1 - 
 = 1 - 0.600 = 0.4
Z
/2
= 1.645
Margin of error = E = Z
/ 2 * 
((
* (1 - 
)) / n)
= 1.645 * (((0.600
* 0.4) / 410)
Margin of error = E = 0.040
A 90% confidence interval for population proportion p is ,
- E < p < 
 + E
0.600 - 0.040 < p < 0.600 + 0.040
0.560 < p < 0.640