In: Statistics and Probability
There is no information at all about the possible proportion of cat lovers in a large population. There's also no time to run a trial poll. A researcher wants to build a 95% confidence interval for the population proportion with the margin of error 3%. The number of the valid answers that the researcher must obtain is
Solution :
Given that,
= 0.5
1 - = 1 - 0.5 = 0.5
margin of error = E = 3% = 0.03
At 95% confidence level the z is ,
= 1 - 95% = 1 - 0.95 = 0.05
/ 2 = 0.05 / 2 = 0.025
Z/2 = Z0.025 = 1.96 ( Using z table )
Sample size = n = (Z/2 / E)2 * * (1 - )
= (1.96 / 0.03)2 * 0.5* 0.5
= 1067.11
Sample size =1067