In a recent poll, 240 people were asked if they liked dogs, and 33% said they did. Find the margin of error of this poll, at the 95% confidence level.
Solution :
Given that,
n = 240
= 33% = 0.33
1 - = 1 - 0.33 = 0.67
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
Margin of error = E = Z / 2 * (( * (1 - )) / n)
= 1.96 * (((0.33 * 0.67) / 240)
= 0.059
Margin of error = 0.059
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