Graphic Presentation of a Frequency Distribution HISTOGRAM A graph in which the classes are marked on the horizontal axis and the class frequencies on the vertical axis. The class frequencies are represented by the heights of the bars, and the bars are drawn adjacent to each other
Graphic Presentation of a Frequency Distribution ▪ A histogram shows the shape of a distribution. ▪ Each class is depicted as a rectangle, with the height of the bar representing the number in each class.
Graphic Presentation of a Frequency Distribution ▪ The horizontal axis represents all possible values, and the bars are adjacent to each other to show the continuous nature of the data
Graphical Presentation of a Frequency Distribution FREQUENCY POLYGON Consists of line segments connecting the points formed by the intersections of the class midpoints and the class frequencies
Graphical Presentation of a Frequency Distribution ▪ A frequency polygon , similar to a histogram, also shows the shape of a distribution. ▪ Class midpoint is the value at the center of a class and represents the typical values in that class
Graphical Presentation of a Frequency Distribution ▪ An advantage of frequency polygon is that it allows direct comparison between two or more distributions.
Cumulative Frequency Distributions CUMULATIVE FREQUENCY POLYGON Develop a cumulative frequency distribution, and portray it graphically in a cumulative frequency polygon
Cumulative Frequency Distributions
Cumulative Frequency Polygon Observations: a) 75% of the vehicles sold earned a profit of $2,300 or less b) 60 of the vehicles sold for a profit of less than $1,600 c) 56% of the vehicles sold for a profit of less than $2,000 (a) (c) (b)
A large internet retailer is studying the lead time for a sample of recent orders. The lead times are reported in days. Try This .... a) How many orders were studied? b) What is the midpoint of the first class? c) What are the coordinates of the first class for a frequency polygon? d) Draw a histogram e) Draw a frequency polygon Lead Time (days) Frequency 0 up to 5 6 5 up to 10 7 10 up to 15 12 15 up to 20 8 20 up to 25 7 Total 40