Argue whether or not you believe using a sample of birds which visit a bird feeder in your yard (the next 50 birds that visit) may or may not yield biased estimates based on the variable being measured/research question being investigated in each of the following situations.
a. Using the proportion of finches (out of 50) that visit the bird feeder to estimate the proportion of finches among all birds that live near your backyard
b. Using the proportion of finches (out of 50) that are at the bird feeder when another finch is also at the bird feeder to estimate the proportion of the time that finches prefer to eat with other finches
c. Using the proportion of male birds (out of 50) that visit the bird feeder to estimate the proportion of male birds among all birds that live near your backyard
d. Using the proportion of male birds that visit the bird feeder to estimate the proportion of male birds that typically visit bird feeders