2022 Introduction to Statistics in Research Mitchell 2nd ed

I N T R O T O R E S E A R C H : D A T A V I S U A L I Z A T I O N & C O M M O N S T A T T E S T S

Comparative Dot Plot

Perhaps one of the simplest visuals is a dot plot. In a comparative dot plot, you use univariate, numerical data with observations from two or more groups. It is the same process as one dot plot, you are just comparing the two-dot plots. In this example, two professors give the same quiz. Each professor grades their class quiz. So the quiz questions are the same, but what do you notice that is different?

Is the distribution in Professor Skew's class symmetric?

No! In dot plot 2, the distribution has a longer tail on the left side. This distribution is negatively skewed. The direction of skewness is always in the direction of the longer tail. Quiz.

What else do you notice?

1) The center of the distribution is larger in Dot Plot 2 (8 instead of 6).

2) There appears to be an unusual observation where one student had 2 answers correct and the next closest observation is 5.

Use visuals that tell a “clear” story

The Human Development Data Center (http://hdr.undp.org/en/data) was created by the United Nations Development Program[me]. Statistical reports are available with over 150 global indicators that can be presented in different combinations. Each tell a story. But a complex one. Here is an excerpt, Dashboard 1 – Quality of Human Development, for over 189 countries and areas. This dashboard contains 14 indicators associated with health and education. It uses a heat- map model using the darker blue as top third, medium blue for the middle third and a light blue representing the bottom third. This dashboard is static and the user can’t interact with it to see specific combinations; however, it does help the user determine quality related to health and education. If you are wondering, United States is ranked seventeenth.

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