In: Statistics and Probability
In Tokyo, 834 Japanese people were asked in a poll on whether they thought the Olympics reduced international tension, increased international tension, or neither. 425 of them said that they thought the Olympics reduced international tension. Calculate a 97.5% confidence interval for the proportion of those who believed this.
Solution :
Given that,
Point estimate = sample proportion =
= x / n = 425 / 834 = 0.510
1 -
= 1 - 0.510 = 0.49
Z/2
= 2.241
Margin of error = E = Z
/ 2 *
((
* (1 -
)) / n)
= 2.241 * (((0.510
* 0.49) / 834)
Margin of error = E = 0.039
A 97.5% confidence interval for population proportion p is ,
- E < p <
+ E
0.510 - 0.039 < p < 0.510 + 0.039
0.471 < p < 0.549
The 97.5% confidence interval for the population proportion p is : 0.471 , 0.549