A survey of 2306 adult Americans aged 18 and older conducted by Harris Interactive found that 417 have donated blood in the past two years.
(a) Obtain a point estimate for the population proportion of adult Americans aged 18 and older who have donated blood in the past two years.
(b) Verify that the requirements for constructing a confidence interval about p are satisfied.
(c) Construct a 90% confidence interval for the population proportion of adult Americans who have donated blood in the past two years.
(d) Interpret the interval.

a) p = 0.1808

b) Since 341.54 ≥ 10. Therefore the requirements for constructing a confidence interval  for p is satisfied.

c) The interval is (0.1676, 0.194)

d) We are 90% confident that the population proportion of adult Americans who have donated blood in the past two years is between 0.1676 and 0.194

Step-by-step explanation:

Given that:

n = 2306 and x =417

a)  Obtain a point estimate for the population proportion (p) is the ratio of sample successes to sample size.

Therefore: p = x / n = 417 / 2306 = 0.1808

p = 0.1808

b) requirements for constructing a confidence interval  for p is given by:

np(1-p) ≥ 10

Therefore: np(1-p) = 2306(0.1808)(1 - 0.1808) = 341.54 ≥ 10

Since 341.54 ≥ 10. Therefore the requirements for constructing a confidence interval  for p is satisfied.

c) c = 90% = 0.9

α = 1 - 0.9 = 0.1

α / 2 = 0.1 /2 = 0.05

From the probability table,

Margin of error (e) =

The boundaries are (p - e, p + e) = (0.1808 - 0.0132, 0.1808 + 0.0132) = (0.1676, 0.194)

The interval is (0.1676, 0.194)

d) We are 90% confident that the population proportion of adult Americans who have donated blood in the past two years is between 0.1676 and 0.194