Video: Using and Interpreting a Bar Chart

A company conducts a survey to find out how professional sports players hydrate during their games. The bar graph shows information about the drink preferences of the sports players. a) In total, what percentage of tennis players did not prefer water? b) Which two groups of sports players had the highest proportion of players who preferred an energy drink? c) Compare the drink preferences of football players and rugby players.

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Video Transcript

A company conducts a survey to find out how professional sports players hydrate during their games. The bar graph shows information about the drink preferences of the sports players. Our bar chart has three categories, water, energy drink, and juice, and four bars representing football, rugby, hockey, tennis for each of those three categories. Part a) In total, what percentage of tennis players did not prefer water?

First of all then, we’re looking for tennis players. So, we’re looking for bars which are dark gray. The method of hydration that we’re interested in is water, and we’re looking for tennis players that did not prefer water. Okay, this is the bar that represents the tennis players who did prefer water for their hydration. The height of that bar is midway between 30 percent of players and 40 percent of players. So, that’s 35 percent of players. That tells us that 35 percent of tennis players prefer water as their method of hydration. That tells us that the rest of the tennis players don’t prefer water. So, if we start off with 100 percent of the tennis players, and we take away the 35 percent who do prefer water, that leaves 65 percent who did not prefer water.

An alternative method would be to add up how many tennis players prefer energy drinks and juice. Looking at the bar for tennis players who prefer an energy drink, we see that 60 percent of tennis players prefer an energy drink. And looking at this bar, we see that five percent of tennis players prefer juice. Adding those together gives us 65 percent that did not prefer water.

Part b) Which two groups of sports players had the highest proportion of players who preferred an energy drink?

That means we’re looking for the two tallest bars within the energy drink category. Of the four bars in the energy drink category, this one is the tallest one. And that represents hockey players because it’s light gray. So, 62.5 percent of hockey players preferred an energy drink to rehydrate. And the second tallest bar in the energy drink category is this one. This is dark gray, which tells us it relates to tennis players. And 60 percent of tennis players prefer an energy drink.

Now, looking at the other two bars, we can see that about 57.5 percent of football players and 45 percent of rugby players preferred an energy drink. So, the two groups of sports players that had the highest proportion of players who preferred an energy drink were hockey players and tennis players.

Now remember, we don’t know the actual number of football, rugby, hockey, or tennis players. These bars are only telling us about the proportions. For example, if there were a million rugby players, then 45 percent of them — that’s 450000 — would prefer an energy drink. But if there are only 100 tennis players, 60 percent of that 100 would be only 60 tennis players that preferred an energy drink. And if that was the case, although there’s a higher proportion of tennis players than rugby players who preferred an energy drink, there would actually be a larger number of rugby players than tennis players who preferred an energy drink. But because our question was only referring to the proportions of the players, we know that the correct answers are hockey players and tennis players.

Now, part c) Compare the drink preferences of football players and rugby players.

Let’s just clear a little bit of space on the screen for our answer. Now, as we just said, we don’t know exactly how many rugby players or football players in total were surveyed. So, we can’t make statements like more or fewer players preferred a particular drink. We can only compare the proportions of each type of player, preferring each type of drink. So, let’s gather some basic data to work with. We can read off from the first bar that 40 percent of footballers prefer water. Somewhere between 50 and 60 percent of them prefer an energy drink. Well, this point here, halfway between 50 and 60, represents 55 percent.

And it looks like the energy drink bar for football players is halfway between 55 and 60. So, that’s 57.5 percent. And football players who prefer juice, well, that’s between zero and 10 percent. This mark here, halfway between zero and 10, represents five percent. And the juice bar seems to be about halfway between zero and five. Which means that around 2.5 percent of football players prefer juice as their hydration method. And using similar methods, about 45 percent of rugby players prefer water. And again, 45 percent of them prefer an energy drink. And 10 percent of rugby players prefer juice.

Now, there are quite a few different things that we could say. For example, looking at water, we could say a higher proportion of rugby players than football players prefer water because 45 percent of rugby players prefer it and only 40 percent of football players prefer it. We could even say that the other way around. A lower proportion of football players than rugby players prefer water.

Next, looking at energy drinks, we could say that a higher proportion of football players than rugby players prefer an energy drink. And looking at juice, we can see that 10 percent of rugby players prefer it while only two and a half percent of football players prefer it. So, we could say a higher proportion of rugby players than football players prefer juice.

So, we can talk about higher proportions or we can turn it round and talk about lower proportions. We could even say something like, “most footballers prefer an energy drink because over 50 percent of footballers prefer an energy drink. But there isn’t a clear favorite amongst rugby players.”

Now, you only need to make two statements. But they do need to be about proportions rather than raw numbers. And they also need to be about different things. For example, you’re not allowed to say, “a higher proportion of rugby players and football players prefer water and a lower proportion of football players than rugby players prefer water” because they’re both saying the same thing. So, there were lots of different statements that you could’ve made. You only need to make two of them, but here are some examples.