A 90% confidence interval for a proportion is given as (0.52,0.58).
It is required to find the sample proportion.
Recall that for confidence interval (x,y), the sample proportion is the midpoint:
[tex]c=\frac{x+y}{2}[/tex]
Substitute x=0.52 and y=0.58 into the equation:
[tex]c=\frac{0.52+0.58}{2}=\frac{1.1}{2}=0.55[/tex]
The answer is C.
