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00:27question 8 before watching this video. This video is based on a question from an actual state exam.
00:34You may have one like this on your state exam. The text in tab A and tab B are the same as for
00:40questions 5 and 6. Please pause the video if you wish to read that information.
00:46Based on the information in figure 1, tab A, and graph 1, tab A, what is the most likely reason
00:52that the scientists measured the beak depth of many individual finches instead of just one?
00:57The answer is choice C, to investigate the variation in beak depth in the finch population.
01:05To know why this is correct, we have to understand the word variation. We'll explain this using an
01:11example dot pets. Are pet dogs heavier than pet cats?
01:18If you said yes, then maybe you were thinking of a pet dog and pet cat like this. If you said no, then
01:25maybe you were thinking of a pet dog like this and a pet cat like this. We're unable to answer this
01:31question with a simple yes or no answer because there are a variety of weights for cats and dogs.
01:36Instead of using the word variety, scientists use the word variation, so we would say there is
01:42variation in the weight of cats and dogs. Both of the words variety and variation are similar to each
01:48other because both mean there can be slight differences from one animal to the next.
01:53If a veterinarian was answering this question, then she or he would take into account the variation
02:00in the weight of the pets. So the veterinarian would answer like this. On average, pet dogs are
02:06heavier than pet cats. The word average is a way to take into consideration that there are some cats
02:11that are heavier than dogs. And there are some dogs that are heavier than cats. But when we look at a lot
02:17of pets, then most of the time the dogs are heavier than the cats. Likewise, when the scientists were
02:22doing research on the finches' beak depths, they could have measured one finch in 1976 and one finch
02:28in 1978. But a better way was to measure many finches in 1976 and then calculate the average beak
02:36depth of those finches. And likewise, to measure many finches in 1978 and calculate their average beak
02:43depth. By measuring many finches, the scientists got an idea of the variation of beak depths.
02:49And by using an average, they were able to summarize the typical beak depth for finches
02:53in 1976 and in 1978. Thanks for your attention.
