Answer: A. 0.50
Step-by-step explanation:
The formula to find the sample size :
, where p= Prior estimate of population proportion.
E= Margin of error
z* =Critical z-value.
When , we do not have prior estimate of population proportion , we use p= 0.5 because at p=0.5 it gives the maximum same sample size for the corresponding confidence interval and margin of error.
Therefore , the conservative value for n can be obtained by using p=0.50.
Therefore , the correct answer is A.0.50 .