Allen's hummingbird (Selasphorus sasin) has been studied by zoologist Bill Alther.+ Suppose a small group of 16 Allen's hummingbirds has been under study in Arizona. The average weight for these birds is x = 3.15 grams. Based on previous studie we can assume that the weights of Allen's hummingbirds have a normal distribution, with o = 0.28 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 (b) What conditions are necessary for your calculations? (Select all that apply. ) O normal distribution of weights O . is known On is large O uniform distribution of weights O . is unknown (c) Interpret your results in the context of this problem. Wa