 The other type of common statistical chart is called a pie chart, or a pie graph, and this allows us to represent fractions corresponding to a given classification. So again, let's take a look at our grade distribution for our class, some number of a's, b's, c's, d's, and f's, and this time maybe we want to construct a pie chart. Now, to determine the fraction of the whole each category represents, we actually need to know how much there is. We have to know the size of our pie, so we'll add up all of the terms in our category, and so we get a total of 25 students here, and notice there's an important distinction between the pie chart and the bar chart. For the pie chart, we actually have to know the total for the bar chart we don't. Now, then we want to express each of these amounts as a fraction of the entirety. So this category A, that's 7 out of 25, and so that's going to be the fraction 725th. Category B, that's 9 out of 25, so the fraction's going to be 925th, and so on. Now, pie charts are a little bit harder to draw by hand than bar charts are, so again, as before, we do want to represent each of these fractions by cutting a pie weight to the correct size, and this is a little bit more problematic. Pie charts are generally very hard to draw accurately without graphing software, especially if the fractions are small, but as with bar charts we want to keep in mind, the size of the pie weight should accurately reflect the magnitudes. Now, here's where it's not worth reducing these fractions. These fractions won't reduce in this particular case, but in general it is not worth reducing the fractions, and if we don't reduce the fractions, we can see that we have a very small wedge of pie here. This is 1 25th of the pie, a slightly larger wedge here, a larger wedge here, and so on. And so with bar charts as with pie charts, we should try to make sure our magnitudes, our relative magnitudes are reflected accurately in the size of the piece. So this 725th, that's going to look like a piece like, well, I didn't all draw it in some amount, and 925th is a slightly larger piece, 625th is a smaller piece, 1 25th is very small piece, and 2 25th is going to be another piece of some particular size. And finally, we'll put all the pieces back together to form the pie, again, labeling each piece. So our pie now looks like this. I'm going to take the A piece, put it back in the pie, our B piece, put it back in the pie, and so on. Actually, if we were constructing this, we would actually go the other way around. We'd start with the pie and then divide it up into the pieces, but the difficulty there is trying to determine how big those pieces are beforehand.