Question: When analyzing the last digits of telephone numbers in Port Jefferson, it is found that among 1000 randomly selected digits, 119 are zeros. If the digits are randomly selected, the proportion of zeros should be 0.100. Test the claim that the proportion of zeroes in the population is random (equal to 0.100).  Edit

Answer: Ho: p = 0.100
Ha: p # 0.100

Critical Values: z = -1.96 or z = +1.96
sample proportion: 119/1000 = 0.119
z(0.119) = (0.119-0.1)/sqrt[0.1*0.9/1000) = 2.0028
Since 2.003 is in the reject interval, reject Ho.  Edit