A researcher wishes to estimate the proportion of adults who have high-speed Internet access. What size sample should be obtained if she wishes the estimate to be within 0.050.05 with 9090% confidence if
a) she uses a previous estimate of 0.36?
b) she does not use any prior estimates?
Answer
(A) given that
sample proportion p = 0.36
margin of error = 0.05
z critical = 1.645 (using z table)
sample size n = ((1-p)*p)*(z/E)^2
= ((1-0.36)*0.36)*(1.645/0.05)^2
= 0.2304*1082.41
= 249.39
= 250 (rounded to next integer)
(B)
given that
margin of error = 0.05
z critical = 1.645 (using z table)
sample size n = 0.25*(z/E)^2
= 0.25*(1.645/0.05)^2
= 0.25*1082.41
= 270.6
= 271 (rounded to next integer)
A researcher wishes to estimate the proportion of adults who have high-speed Internet access. What size...
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