Question

Bill Alther is a zoologist who studies Anna's hummingbird (Calypte anna).† 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 x = 3.75 grams. Let x be a random variable representing weights of hummingbirds in this part of the Grand Canyon. We assume that x has a normal distribution and σ = 0.98 gram. Suppose it is known that for the population of all Anna's hummingbirds, the mean weight is μ = 4.80 grams. Do the data indicate that the mean weight of these birds in this part of the Grand Canyon is less than 4.80 grams? Use α = 0.10.

A) State the null and alternate hypotheses. Will you use a left-tailed, right-tailed, or two-tailed test?

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

C) Compute the z value of the sample test statistic. (Round your answer to two decimal places.)

D)  Find (or estimate) the P-value. (Round your answer to four decimal places.)

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

F) State your conclusion in the context of the application.

There is sufficient evidence at the 0.10 level to conclude that humming birds in the Grand Canyon weigh less than 4.80 grams.

There is insufficient evidence at the 0.10 level to conclude that humming birds in the Grand Canyon weigh less than 4.80 grams.    

Answer 1

a)

null hypothesis:Ho		μ	=	4.8
Alternate Hypothesis:Ha		μ	<	4.8

left tailed

b)

sampling distribution will you use? z distribution as population is normally distributed and population std deviation is known

c)

z value of the sample test statistic =-2.62

d)

p value =0.0044

e)

reject the null hypothesis

the data are statistically significant at level α

f)

There is sufficient evidence at the 0.10 level to conclude that humming birds in the Grand Canyon weigh less than 4.80 grams.