Question

For this problem, carry at least four digits after the decimal in your calculations. Answers may vary slightly due to rounding. In a random sample of 63 professional actors, it was found that 38 were extroverts. A button hyperlink to the SALT program that reads: Use SALT. (a) Let p represent the proportion of all actors who are extroverts. Find a point estimate for p. (Round your answer to four decimal places.) Incorrect: Your answer is incorrect. (b) Find a 95% confidence interval for p. (Round your answers to two decimal places.) lower limit Incorrect: Your answer is incorrect. upper limit Incorrect: Your answer is incorrect.

Answer 1

Answer:

a) 0.6032

b)

Lower limit: 0.48

Upper limit: 0.72

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 $1 - \frac{\alpha}{2}$.

Question a:

In a random sample of 63 professional actors, it was found that 38 were extroverts.

We use this to find the sample proportion, which is the point estimate for p. So

$\pi = \frac{38}{63} = 0.6032$

Question b:

Sample of 63 means that $n = 63$

95% confidence level

So $\alpha = 0.05$, z is the value of Z that has a pvalue of $1 - \frac{0.05}{2} = 0.975$, so $Z = 1.96$.

The lower limit of this interval is:

$\pi - z\sqrt{\frac{\pi(1-\pi)}{n}} = 0.6032 - 1.96\sqrt{\frac{0.6032*0.3968}{63}} = 0.4824$

The upper limit of this interval is:

$\pi + z\sqrt{\frac{\pi(1-\pi)}{n}} = 0.6032 + 1.96\sqrt{\frac{0.6032*0.3968}{63}} = 0.724$

Rounding to two decimal places:

Lower limit: 0.48

Upper limit: 0.72