In: Statistics and Probability
In a sample of 1901 patients who underwent a certain type of
surgery, 22% experienced complications. Find a 90% confidence
interval for the proportion of all those undergoing this surgery
who experience complications.
Solution :
Given that,
Point estimate = sample proportion = = 0.22
1 - = 1- 0.22 =0.78
At 90% confidence level
= 1 - 90%
= 1 - 0.90 =0.10
/2
= 0.05
Z/2
= Z0.05 = 1.645 ( Using z table )
Margin of error = E Z/2 *(( * (1 - )) / n)
= 1.645 *((0.22*0.78) / 1901)
E = 0.016
A 90% confidence interval for population proportion p is ,
- E < p < + E
0.22-0.016 < p < 0.22+0.016
0.204< p < 0.236