1.2 Displaying Quantitative Data with graphs 08.24.2017

Homework Questions? Remember, I will give you points for completion, not accuracy

Now on to New Stuff

Now on to New Stuff How to describe: Shape: how many peaks? Is one tail longer than the other (skewed)? Center: where is the center point (or the median)? Spread: minimum and maximum Outliers: Are there any outliers? SOCS

Shape Symmetric Skewed (to the right)

Center Where is the center? (roughly)

Center Where is the center? (roughly) Roughly 7.5 pounds

Outliers For now, we will assess whether something is an outlier visually Does it look like there are any outliers? Later, we will learn a rule for calculating it

Spread The easiest way to describe the spread is simply to state the minimum value and the maximum value

An Example Describe the distribution The distribution is single- peaked and skewed to the right, with probable outliers at 55, 38, and two possible outliers at 29. The center is roughly 7 electoral votes, with a minimum of 3 and a maximum of 55.

You try Describe the distribution

You try Describe the distribution The distribution is single- peaked and skewed to the left. There do not appear to be any outliers. The center of the distribution is around 73, with a minimum of about 46 and a maximum of about 83.

Stemplots I do not like them I do not find them helpful But you’re expected to know what they are Does anyone know what a stemplot is?

Stemplots Let’s say that the class gets the following test grades: 42, 67, 73, 78, 82, 84, 86, 91, 91, 94, 99 The Stemplot would look like

Stemplots You can also use a stemplot to compare two different datasets

Histograms The most common graph of a quantitative variable Also, in my opinion, the most useful Similar to a dotplot, but for larger datasets

Histograms Notice that this is telling us the same information as a dotplot Just larger counts Looks a bit cleaner to some people

Histograms However, there are problems with histograms Our eyes respond to the area of the bars Can be confused with a bar graph Bar graph is for categorical variables Other problems (see pages 39-41)

You try Make a histogram for the following data: Average first serve speed for 21 professional tennis players: 124.5, 122.1, 120.3, 119.7, 118.7, 116.5, 115.6, 114.5, 114, 113.9, 113.7, 112.6, 112.4, 112.3, 112.2, 110.5, 109.4, 108.3, 107.3, 103.1, 101.9

HW Time