Question

Researchers in the 1990’s determined that the average bill length of birds living in a forest was 22.5mm. This information was published but the actual data was lost. Now, a college student is interested in determining if the bill length of these birds has changed over time. She randomly traps 25 individuals, measures each one, and the mean length is 21.8mm, with a standard deviation (s) of 2.5mm.

1. What is the most appropriate statistical test to determine if the mean bill length of these birds has changed?

Now the researcher above wanted to compare the bill length of male vs female birds from her sample of 25 birds. She checked the assumption of normality and the data was normal and there were no major outliers.

1. What is the best test for her to use to compare the weight between the sexes?  

2. What would have been the best test for her to use if the bill length data was not normal?

Answer 1

1. What is the most appropriate statistical test to determine if the mean bill length of these birds has changed?

The most appropriate statistical test to determine if the mean bill length of these birds has changed is the one-sample t-test.

1. What is the best test for her to use to compare the weight between the sexes?  

The best test for her to use to compare the weight between the sexes is the independent-samples t-test.

2. What would have been the best test for her to use if the bill length data was not normal?

The best test for her to use if the bill length data was not normal is the Man-Whitney test.