I. Assume that an ecologist is studying the effects of the insecticide DDT on wi

Question

I. Assume that an ecologist is studying the effects of the insecticide DDT on wild birds in Sumatra. DDT sprayed on insects and vegetation subsequently eaten by female birds seems to affect the thickness of their eggshells and thus affects the protection of the embryonic birds. Assume the ecologist knows that the mean eggshell thickness in untreated birds (birds that have not eaten matter sprayed with DDT) is 330 microns and the variance is 2500 microns squared. Assume also that the thickness follow a normal distribution. The ecologist takes a sample of 16 eggshells and finds a sample mean of 290. The ecologist is interested in seeing if the spraying of DDT has any effect on the eggshells. ( = .05 ) a.) State the null and alternative hypotheses for this test situation. Ho: a. b.) Test statistic: c.) Graph: d.) Conclusion: ) Construct a 95% C.1. for the mean.

Explanation / Answer

a)
Below are the null and alternate hypothesis
H0: mu = 330
H1: mu not equals to 330 (as ecologist is interested in finding any effect on eggshell thickness)

b)
Test statitstics,
t = (290 - 330)/(sqrt(2500/16)) = -3.2

c)
p-value = 0.00596
As this is two tailed test, we have rejection region in on both sides of the graph beyond +/- 1.96

d)
As p-value is less than significance level of 0.05, we reject the null hypothesis
This means there are significant evidence to conclude that there DDT has effect on the eggshells.

e)

CI for 95% n 16 mean 290 z-value of 95% CI 1.9600 std. dev. 50 SE = std.dev./sqrt(n) 12.50000 ME = z*SE 24.49955 Lower Limit = Mean - ME 265.50045 Upper Limit = Mean + ME 314.49955 95% CI (265.5005 , 314.4995 )

Related Questions

Navigate

• Browse (All)
• Browse I
• Subjects

---