Descriping Data: Frequency Distributions and Graphic Presentation

1. A Frequency Distribution is a grouping of data into mutually exclusive classes showing the number of observation in each class.
1. a step in constructing a frequency distribution are:
1. Decide how many classes you wish.
2. Determine the class interval or width.
3. Set the individual class limits.
4. Tally the raw data into the classes.
5. Count the number of tallies in each class.
   
2. the class frequency is the number of observation in each class.
3. the class interval is the difference between the limits of two consecutive classes.
4. the class midpoint is halfway between the limits of two consecutive Classes.
   
2. A relative frequency distribution shows the percent of the observations in each class.
3. There are three methods for graphically portraying a frequency distribution:
1. A histogram portrays the number of frequencies in each class in the form of rectangles.
2. A frequency polygon consists of line segments connecting the points formed by the intersections of the class midpoints and the class frequencies.
3. A cumulative frequency polygon shows the number of observations below a certain Value.
   
4. There are many charts used in newspapers and magazines:
1. A line chart is ideal for showing the trend of a variable such as sales or income overtime.
2. Bar charts are similar to line charts and are useful for showing changes in nominal scales data.
3. Pie charts are useful for showing the percent that various components are of the total.