chapter 11- frequency distributions and histograms

Histogram

A bar trap expect-

• the bars touch (a continuous type)

• The width of each bar is the same and represents a quantitative value (age, years, length)

• Number of classes (bars) should be between 5 and 15

The width of each class (bar) is the class width, CW- the next highest integer.

For a histogram, the midpoint is used to

scale the horizontal axis

Class boundary

Halfway between the upper limit of one class and the lower limit of the next.

Drawing the bars from class boundary to class boundary will assure the bars touch

the lowest lower class boundary is the low data values minus 0.5 (each successive class boundary is found by adding the class width to the previous class boundary)

Stem and leaf display

Gives much of the same information as a histogram

• Used to rank-order and arrange data.

• Show information similar to a bar but retain original data values

• Accuracy requires the digits of each leaf unit be of equal width

• EVERY VALUE MAINTAINS ITS NUMBER

Right skewed

Also knocked as positively skewed

Data-

• Salaries (how much they make)

• Ages

Left skewed

also known as negatively skewed

Data-

• Number days of snowfall

• Grades on a test

• Life expectancy

Symmetric Graph