In a random sample of 1000 students, 80% were in favor of longer hours at the school library.
What is the standard error of the sample proportion?
Calculate the margin of error. Calculate a 95% confidence interval for proportion of students favoring longer library hours. Interpret.
Solution :
Given that,
Point estimate = sample proportion = = 0.80
1 - = 0.20
Z/2 = 1.96
standard error = (((0.80 * 0.20) /1000 ) = 0.1265
Margin of error = E = Z / 2 * (( * (1 - )) / n)
= 1.96 * (((0.80 * 0.20) /1000 )
= 0.025
A 95% confidence interval for population proportion p is ,
- E < p < + E
0.80 - 0.025 < p < 0.80 + 0.025
0.775< p < 0.825
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