1 Graphical Descriptions of Data
2 Lessons • Frequency Distributions • Graphical Displays of Data: Pie Charts and Bar Charts • Graphical Displays of Data: Histograms, Polygons, Stem and Leaf Plots • Analyzing Graphs
3 Frequency Distributions
4 Objectives • Learn how to construct a frequency distribution. • Know the characteristics of a frequency distribution.
5 Introduction • After collecting data you need to organize it so that inferences and conclusions can be made. • Raw data is not useful if you want to know the lowest price or the average.
6 Introduction • If we create an ordered array then we can easily see the lowest price and the highest price • Which price is common? • Is there a pattern to the data?
7 Constructing a Frequency Distribution • A distribution displays data values that occur and how frequently each value occurs. • A frequency distribution is a table that divides the data into groups, called classes , and shows how many data values occur in each group. • The frequency , f , of a group, or class, is the number of data values in that class.
8 Constructing a Frequency Distribution • Ungrouped Frequency Distributions – A frequency distribution where each class represents a single value. – Ideal when the data set is relatively small, or contains only a few possible values. – E.g., the distribution of letter grades A, B, C, D, F.
9 Constructing a Frequency Distribution • Grouped Frequency Distribution – A frequency distribution where the classes are ranges of possible values. – Ideal with large data sets containing many different values for the variable. – E.g., if we used ungrouped frequency distribution for our refrigerator example we would have 20 classes. A grouped frequency distribution will result in fewer classes hence more manageable.
10 Constructing a Frequency Distribution Steps for Constructing a Frequency Distribution 1. Decide how many classes should be in the distribution. 2. Choose an appropriate class width. 3. Find the class limits. 4.Determine the frequency of each class.
You've reached the end of your free preview.
Want to read all 86 pages?
- Fall '18
- F. TAILOKA
- Frequency, Frequency distribution, Bar chart, Histogram