In: Statistics and Probability
Wildlife biologists inspect 128 deer taken by hunters and find 23 of them carrying ticks that test positive for Lyme disease. a) Create a 90% confidence interval for the percentage of deer that may carry such ticks.
Solution :
Given that,
n = 128
x = 23
Point estimate = sample proportion =
= x / n = 23/128=0.180
1 -
= 1-0.180=0.820
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 (((0.180*0.820)
/128 )
= 0.0559
A 90% confidence interval for population proportion p is ,
- E < p <
+ E
0.180-0.0559 < p <0.180+ 0.0559
0.1241< p < 0.2359
The 90% confidence interval for the population proportion p is : 0.1241,0.2359