Wednesday, June 27, 2012

Brass Polishing Distribution

The door from the terrace to the cafe at the De Young museum in San Francisco. Many hands have entered, polishing the pole. Few grab it low, few grab it high. Most open the door at about elbow height. The resulting wear pattern shows a distribution of this height.

Monday, June 25, 2012

MOMA Height Exhibit

Here is a proper depiction of a height distribution. From the exhibit "Performance 4: Roman Ondák" that was at the Museum of Modern Art in 2009.

Of course, Sir Francis Galton had this idea over a century ago. See his book on Hereditary Genius on page 28.

Friday, June 22, 2012

Curve (maybe), Distribution NO.

Found on Flickr with the caption "Standard Normal Distribution".

Perhaps it is suggestive of histogram bars often seen with a bell-shape of a normal distribution. But what variable is being measured? See "NO, NO, NO, the Wrong Idea" in the previous post here.

Tuesday, June 19, 2012

NO, NO, NO. The wrong idea.

Found on Flickr here with the caption "normal distribution class photo".

A bell-shaped normal curve is not the normal distribution. The curve only describes the distribution. A normal distribution is a particular arrangement of measurements on a number line.

This photo seems to want to depict a normal distribution of the heights of students. If height is the variable of interest, the horizontal axis should be a number line with all the smallest students on the left and those taller would be placed further to the right. If the heights of the students had a bell-shaped histogram we would expect to see very few short students, very few tall students, and most of the students would have heights that fall between those extremes. This photo puts the tall students in the middle and shorter ones on the extremes. Maybe they have illustrated a bell-curve, but no number line is used, so no distribution (normal or otherwise) could be represented.