Question

In a recent survey, a random sample of 130 families were asked about whether they have a pet, and 67 reported that they have a pet. What value of z should be used to calculate a confidence interval with a 90% confidence level

Answer 1

Answer:

z = 1.645 should be used.

Step-by-step explanation:

In a sample with a number n of people surveyed with a probability of a success of $\pi$, and a confidence level of $1-\alpha$, we have the following confidence interval of proportions.

$\pi \pm z\sqrt{\frac{\pi(1-\pi)}{n}}$

In which

z is the zscore that has a pvalue of $1 - \frac{\alpha}{2}$.

90% confidence level

So $\alpha = 0.1$, z is the value of Z that has a pvalue of $1 - \frac{0.1}{2} = 0.95$, so $z = 1.645$.

z = 1.645 should be used.