Jan. 23 Statistic for the Day: Average Number of Times an American Opens the Refrigerator Each Day: 22 Assignment: Having read Chapter 9, go back and study it closely. Exercises p : 1, 2, 4, 5, 9 These slides were created by Tom Hettmansperger and in some cases modified by David Hunter Source: Harper’s Magazine

Recall Research Question or Hypothesis Research Question or Hypothesis Quantification Quantification Collect data Collect data Analyze data Analyze data Conclusions and/or action Conclusions and/or action

As first step in extracting information from data use graphics or pictures: Boxplot Boxplot  Stem and leaf  Median and quartiles Histogram or normal curve Histogram or normal curve  Mean and standard deviation

Boxplot

Overlapping Histograms

Histogram with Normal Curve

Scatter Plot for two measurements: RELATIONSHIP

US Pop and Violent Crime Table 9.2 p155 text Year US Pop No. crimes In millions

If we want to suggest a much more dramatic increase:

Enrolment in higher education As percent of population

Moral of the story: Whenever you meet a graph that is very far from square, it is likely to produce an impression different from what you would have obtained from the data themselves.

Almost any graph in which the vertical scale does not start with zero is deceptive. Another moral:

This Is a Good Bar Graph

BAD

The problem with the pens is that it is the heights that should be compared. But instead, we end up comparing the areas. The areas do not make the correct comparison.

GOOD But with an error

The letters are good because each letter represents an amount. However, one should use the correct number of letters

Bogus vertical scale. Hard to say what the graph should look like.

Portion of income taken by the government. Top: spending equal to the income in western states. Bottom: more densely populated east.

Some people think it means that rhinos have gotten smaller!