In the Focus Problem at the beginning of this chapter, a study was described com
ID: 3223382 • Letter: I
Question
In the Focus Problem at the beginning of this chapter, a study was described comparing the hatch ratios of wood duck nesting boxes. Group I nesting boxes were well separated from each other and well hidden by available brush. There were a total of 455 eggs in group I boxes, of which a field count showed about 278 hatched. Group II nesting boxes were placed in highly visible locations and grouped closely together. There were a total of 780 eggs in group II boxes, of which a field count showed about 278 hatched. (a) Find a point estimate p1 for p1, the proportion of eggs that hatch in group I nest box placements. (Round your answer to three decimal places.) p1 = Incorrect: Your answer is incorrect. . Find a 90% confidence interval for p1. (Round your answers to three decimal places.) lower limit upper limit (b) Find a point estimate p2 for p2, the proportion of eggs that hatch in group II nest box placements. (Round your answer to three decimal places.) p2 = Find a 90% confidence interval for p2. (Round your answers to three decimal places.) lower limit upper limit (c) Find a 90% confidence interval for p1 p2. (Round your answers to three decimal places.) lower limit upper limit Does the interval indicate that the proportion of eggs hatched from group I nest boxes is higher than, lower than, or equal to the proportion of eggs hatched from group II nest boxes? We can not make any conclusions using this confidence interval. Because the interval contains only negative numbers, we can say that a higher proportion of eggs hatched in highly visible, closely grouped nesting boxes. Because the interval contains both positive and negative numbers, we can not say that a higher proportion of eggs hatched in well-separated and well-hidden nesting boxes. Because the interval contains only positive numbers, we can say that a higher proportion of eggs hatched in well-separated and well-hidden nesting boxes. (d) What conclusions about placement of nest boxes can be drawn? In the article discussed in the Focus Problem, additional concerns are raised about the higher cost of placing and maintaining group I nest box placements. Also at issue is the cost efficiency per successful wood duck hatch. No conclusion can be made. A greater proportion of wood duck eggs hatch if the eggs are laid in well-separated, well-hidden nesting boxes. A greater proportion of wood duck eggs hatch if the eggs are laid in highly visible, closely grouped nesting boxes. The eggs hatch equally well in both conditions.
Explanation / Answer
let X1 = field count showed about 278 hatched.
n1 = There were a total of 455 eggs in group I boxes.
X2 = field count showed about 278 hatched.
n2 = There were a total of 780 eggs in group I boxes.
a) from minitab software
Sample X1 n1 Sample p_hat 90% CI
1 278 455 0.611 (0.573, 0.649)
b)
Sample X2 n2 Sample p2-hat 90% CI
2 278 780 0.356 (0.328, 0.385)
c)
Test and CI for Two Proportions
Sample X N Sample p-hat
1 278 455 0.611
2 278 780 0.356
Difference = p (1) - p (2)
Estimate for difference: 0.255
90% CI for difference: (0.208, 0.302)
Test for difference = 0 (vs not = 0): Z = 8.91 P-Value = 0.000
d)