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 68 professional actors, it was found that 37 were extroverts.

(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.)

(b)

Find a 95% confidence interval for p. (Round your answers to two decimal places.)
lower limit   
upper limit   

Give a brief interpretation of the meaning of the confidence interval you have found.

We are 95% confident that the true proportion of actors who are extroverts falls outside this interval. We are 95% confident that the true proportion of actors who are extroverts falls within this interval.     We are 5% confident that the true proportion of actors who are extroverts falls above this interval. We are 5% confident that the true proportion of actors who are extroverts falls within this interval

(c)

Do you think the conditions n·p > 5 and n·q > 5 are satisfied in this problem? Explain why this would be an important consideration.

No, the conditions are not satisfied. This is important because it allows us to say that p̂ is approximately normal. Yes, the conditions are satisfied. This is important because it allows us to say that p̂ is approximately normal.     Yes, the conditions are satisfied. This is important because it allows us to say that p̂ is approximately binomial. No, the conditions are not satisfied. This is important because it allows us to say that p̂ is approximately binomial.

Answer 1

(a)

Here point estimate of p = 37/68 = 0.5441

(b)

95% confidence interval= p +- z_95% sqrt [p * (1-p)/n]

= 0.544 +- 1.96 * sqrt [0.544 * (1 - 0.544)/69]

= 0.544 +- 0.118

= (0.426, 0.662)

Lower Limit = 0.426

Upper Limit = 0.662

We are 95% confident that the true proportion of actors who are extroverts falls within this interval.

(c) Here Yes, the conditions are satisfied. This is important because it allows us to say that p̂ is approximately normal.