In a government study of financial aid for college students, it becomes necessary to estimate the percentage of full-time college students who earn a bachelor's degree in four years or less. Find the sample size necessary to limit the margin of error to 5% at the 95% confidence level.
Solution:
Given that,
= 0.5
1 - = 1 - 0.5 = 0.5
margin of error = E = 5% = 0.05
At 95% confidence level the z is ,
= 1 - 95% = 1 - 0.95 = 0.05
/ 2 = 0.05 / 2 = 0.025
Z/2 = Z0.025 = 1.960
Sample size = n = ((Z / 2) / E)2 * * (1 - )
= (1.960 / 0.05)2 * 0.5 * 0.5
= 384.16
= 384
n = sample size = 384
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