Allen's hummingbird (Selasphorus sasin) has been studied by zoologist Bill Alther.† Suppose a small group of 10 Allen's hummingbirds has been under study in Arizona. The average weight for these birds is x = 3.15 grams. Based on previous studies, we can assume that the weights of Allen's hummingbirds have a normal distribution, with σ = 0.26 gram.
(a) Find an 80% confidence interval for the average weights of Allen's hummingbirds in the study region. What is the margin of error? (Round your answers to two decimal places.)
lower limit | |
upper limit | |
margin of error |
(d) Find the sample size necessary for an 80% confidence level
with a maximal margin of error E = 0.11 for the mean
weights of the hummingbirds. (Round up to the nearest whole
number.)
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