In: Statistics and Probability
The head of a computer science department is interested in
estimating the proportion of students entering the department who
will choose the new computer engineering option. A preliminary
sample indicates that the proportion will be around
0.208.
What size sample should the department head take if she wants to be
95% confident that the estimate is within 0.02 of
the true proportion?
Solution :
Given that,
= 0.208
1 - = 1 - 0.208 = 0.792
margin of error = E = 0.02
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 / 0.02)2 * 0.208 * 0.792
= 1582.12
Sample size =1582