Question

1. Bill Alther is a zoologist who studies Anna's hummingbird (Calypte anna). (Reference: Hummingbirds, K. Long, W. Alther.) Suppose that in a remote part of the Grand Canyon, a random sample of six of these birds was caught, weighed, and released. The weights (in grams) were as follows. 3.7 2.9 3.8 4.2 4.8 3.1

The sample mean is = 3.75 grams. Let x be a random variable representing weights of hummingbirds in this part of the Grand Canyon. We assume that xhas a normal distribution and σ = 0.64 gram. Suppose it is known that for the population of all Anna's hummingbirds, the mean weight is μ = 4.30 grams. Do the data indicate that the mean weight of these birds in this part of the Grand Canyon is less than 4.30 grams? Use α = 0.10.

1 (a) What is the level of significance? =_______(Enter a number.) State the null and alternate hypotheses. Will you use a left-tailed, right-tailed, or two-tailed test?

a. H0: μ = 4.3 g; H1: μ < 4.3 g; left-tailed

b. H0: μ = 4.3 g; H1: μ ≠ 4.3 g; two-tailed

c. H0: μ = 4.3 g; H1: μ > 4.3 g; right-tailed

d. H0: μ < 4.3 g; H1: μ = 4.3 g; left-tailed

1(b) What sampling distribution will you use? Explain the rationale for your choice of sampling distribution.

a. The Student's t, since n is large with unknown σ.

b. The standard normal, since we assume that x has a normal distribution with unknown σ.

c. The Student's t, since we assume that x has a normal distribution with known σ.

d. The standard normal, since we assume that x has a normal distribution with known σ.

Compute the z value of the sample test statistic. =_____(Enter a number. Round your answer to two decimal places.)

1(c) Find (or estimate) the P-value. (Enter a number. Round your answer to four decimal places.) Sketch the sampling distribution and show the area corresponding to the P-value. (Select the correct graph.)

1(d) Based on your answers in parts (a) to (c), will you reject or fail to reject the null hypothesis? Are the data statistically significant at level α?

a. At the α = 0.10 level, we reject the null hypothesis and conclude the data are statistically significant.

b. At the α = 0.10 level, we reject the null hypothesis and conclude the data are not statistically significant.

c. At the α = 0.10 level, we fail to reject the null hypothesis and conclude the data are statistically significant.

d. At the α = 0.10 level, we fail to reject the null hypothesis and conclude the data are not statistically significant.

1(e) State your conclusion in the context of the application.

a. There is sufficient evidence at the 0.10 level to conclude that humming birds in the Grand Canyon weigh less than 4.30 grams.

b. There is insufficient evidence at the 0.10 level to conclude that humming birds in the Grand Canyon weigh less than 4.30 grams.

2. Suppose you want to test the claim that a population mean equals 34.

2(a) State the null hypothesis.

a. H₀: μ > 34

b. H₀: μ < 34     

c. H₀: μ = 34

d. H₀: μ ≠ 34

e. H₀: μ ≥ 34

2(b)State the alternate hypothesis if you have no information regarding how the population mean might differ from 34.

a. H₁: μ > 34

b. H₁: μ < 34     

c. H₁: μ = 34

d. H₁: μ ≠ 34

e. H₁: μ ≥ 34

2(c) State the alternative hypothesis if you believe (based on experience or past studies) that the population mean may exceed 34.

a. H₁: μ > 34

b. H₁: μ < 34     

c. H₁: μ = 34

d. H₁: μ ≠ 34

e. H₁: μ ≥ 34

2(d)  State the alternative hypothesis if you believe (based on experience or past studies) that the population mean may be less than 34.

a. H₁: μ > 34

b. H₁: μ < 34     

c. H₁: μ = 34

d. H₁: μ ≠ 34

e. H₁: μ ≥ 34

Answer 1

a)

level of significance =

0.1

a. H0: μ = 4.3 g; H1: μ < 4.3 g; left-tailed

b)

d. The standard normal, since we assume that x has a normal distribution with known σ.

population mean μ=		4.3
sample mean 'x̄=		3.750
sample size    n=		6
std deviation σ=		0.640
std error ='σx=σ/√n=0.64/√6=		0.2613
z statistic= ='(x̄-μ)/σx=(3.75-4.3)/0.261=		-2.11

c)

p value        =

0.0174

(from excel:1*normsdist(-2.11)

d)

a. At the α = 0.10 level, we reject the null hypothesis and conclude the data are statistically significant.

e)

a. There is sufficient evidence at the 0.10 level to conclude that humming birds in the Grand Canyon weigh less than 4.30 grams.

2a)

c. H₀: μ = 34

2b)

d. H₁: μ ≠ 34

2c)

a. H₁: μ > 34

2d)

b. H₁: μ < 34