Respuesta :
Answer:
The LCL for a 90% confidence interval for p is 0.82.
Step-by-step explanation:
In a sample with a number n of people surveyed with a probability of a success of [tex]\pi[/tex], and a confidence level of [tex]1-\alpha[/tex], we have the following confidence interval of proportions.
[tex]\pi \pm z\sqrt{\frac{\pi(1-\pi)}{n}}[/tex]
In which
z is the zscore that has a pvalue of [tex]1 - \frac{\alpha}{2}[/tex].
A lawn service owner is testing new weed killers. He discovered that a particular weed killer was effective 89% of time. Suppose that this estimate was based on a random sample of 60 applications.
This means that [tex]\pi = 0.89, n = 60[/tex]
90% confidence level
So [tex]\alpha = 0.1[/tex], z is the value of Z that has a pvalue of [tex]1 - \frac{0.1}{2} = 0.95[/tex], so [tex]Z = 1.645[/tex].
The lower limit of this interval is:
[tex]\pi - z\sqrt{\frac{\pi(1-\pi)}{n}} = 0.89 - 1.645\sqrt{\frac{0.89*0.11}{60}} = 0.8236[/tex]
Rounding to two decimal places, the LCL for a 90% confidence interval for p is 0.82.
