What proportion of all americans believe the president is doing a good job? a recent poll found that 39% of 1000 randomly selected americans approved of the way george w. bush is handling his job as president.
a.does this mean that only 39% of all americans approve of the way george w. bush is handling his job as president?
b.for a sample proportion, as long as the population is greater than ten times the sample size, we can approximate the standard deviation to be what is the standard deviation for this sample?
c.what is the critical value for a 90% confidence interval?
d.what is the critical value for a 95% confidence interval?
e.what is the 90% confidence interval? be sure to include the formula with your numbers plugged in. use the model: f) what is the 95% confidence interval?

a. Since it is a few selected 1000 Americans in the survey, it is more of a sample thing and it's too small to determine for whole of america.
b. Standard deviation = square root of p(1-p)/n, p is 39/100, n = 1000 SD =square root of 0.39 (1 - 0.39) / 1000 => SD = square root of 0.2379 /
1000
SD = 0.0154
c. From the z value table critical avlue for a 90% confidence interval is 1.645
d. From the z value table critical avlue for a 95% confidence interval is 1.96
e. For 90% z = 1.645, P = 0.39, SD = 0.0154
CI = P +- z(SD) => CI = 0.39 +- 1.645(0.154) => 0.39 +- 0.0253
So the interval is (0.364, 0.415)
f. For 95% z = 1.96, P = 0.39, SD = 0.0154
CI = P +- z(SD) => CI = 0.39 +- 1.96(0.154) => 0.39 +- 0.0302
So the interval is (0.359, 0.420)