Data to justify experimental claims examples | High school biology | Khan Academy

What we have here are a few data analysis questions in a biology context from the New York Regents exam. But these are useful example problems if you're studying high school biology in general because they might show up in some type of an exam that your teacher gives you, or you might see on a standardized test.

A student proposes that if volunteers warm up before squeezing a clothespin for one minute, they will increase the number of times that they can squeeze it without tiring. He states that this is because their muscles will be better prepared for the exercise. The data from an experiment are shown in the data table below.

Which trial from the chart above provides the best data to support his claim? Support your answer. So pause this video and see if you could answer it.

So let's just make sure we understand what's going on here. There are two trials. This is the first trial (trial one) right over here. In trial one, you had two groups of 10 students. One of them did warm up, and the other ones—another 10—did not warm up.

In trial two, you had two more groups, and this time there were groups of 25. Once again, 25 who did warm up and 25 who didn't warm up. Now, in trial one, the group that warmed up actually had a lower number of average squeezes. So this goes against the hypothesis that the student had. The hypothesis the student had was if they warm up beforehand, then you'd actually be able to do more squeezes.

So trial one actually goes against the student's claim. Trial two seems to slightly go in favor of the student's claim. The group that warmed up was able to eke out a few more. Now we haven't done the statistical analysis to know how probable this is and if it was due purely to random chance. But just to answer that question: trial one goes a little bit against the student's claim. Trial two best supports this claim, although it doesn't do it so strongly.

So I would say trial two, and that is because the 25 that warmed up—that is group three—were able, on average, to squeeze more in a minute than group four, who didn't warm up.

All right, let's do another question here. So here we're told students were asked to design a lab that investigated the relationship between exercise and heart rate. Heart rate was determined by recording the pulse rate in beats per minute. The students hypothesized that increased exercise results in an increased heart rate. The class results for the experiment are shown in the graph below.

Then they say, which statement is best supported by this graph? We're given four choices—so pause this video and see if you can answer this on your own.

All right, now let's go through statement by statement. Statement one: before exercising, the average pulse rate was 65. Four minutes after exercising, the average pulse rate was 65. So let's see. Before exercising, the average pulse rate was 65. This is for the time period right over here, and it does look like over most of that time period—let me just mark it in red—it does look like that is roughly true.

It looks like the average pulse rate was 65. But now let's read the second part of the statement: four minutes after exercising, the average pulse rate was 65 as well. Four minutes after exercising, what's the average pulse rate? Well, it sure isn't 65. It looks closer to being maybe 135, not 65. So we could rule this one out.

After four minutes of exercising, the average pulse rate was 120. Let's see, after four minutes—this is when the exercise starts—after four minutes, the average pulse rate was 120. No, it looks like it was closer to 135 or something like this. So this is already looking fishy.

Two minutes after exercising, the average pulse rate was 120. So two minutes after exercising, the average pulse rate actually seems closer to about 90. So both of those look fishy. I'll rule that one out.

While exercising, the highest average pulse rate was 150. Before exercising, the average pulse rate was 65. So let's see. While exercising, the highest average pulse rate happens right over there, and that does indeed look pretty close to 150. So this part's looking good. Before exercising, the average pulse rate was 65—we already talked about this part.

So this is looking good. I'm liking this choice. But let's see choice four: two minutes before exercising, the average pulse rate was 80. So two minutes before exercising, this is when we start exercising, and each of these hash marks is a minute. So two minutes before, the average pulse rate was not 80. So that's false.

Two minutes after exercise, the average pulse rate was 140. After two minutes, the average pulse rate was also not 140. So both of those statements are not correct.

So I like statement three; that's the one that seems to be backed up by the data here.