Descriptive Statistics, Part Two

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# Descriptive Statistics, Part Two - PowerPoint PPT Presentation

Descriptive Statistics, Part Two. Farrokh Alemi, Ph.D. Kashif Haqqi, M.D. Objectives Frequency distribution Categorical Ungrouped Grouped. Histogram Cumulative frequency Pie chart Bar chart. Table of Content. Objectives.

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## Descriptive Statistics, Part Two

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### Descriptive Statistics, Part Two

Farrokh Alemi, Ph.D.

Kashif Haqqi, M.D.

Objectives

Frequency distribution

Categorical

Ungrouped

Grouped

Histogram

Cumulative frequency

Pie chart

Bar chart

Table of Content
Objectives
• Given a set of nominal or ordinal data, interpret its frequency distribution, pie chart, and bar chart.
• Given a set of numerical data, interpret its frequency distribution, cumulative frequency distribution, and histogram.
• Given a set of numerical data, interpret the meaning of its range, variance, standard deviation, and coefficient of variation.

Organizing Data
• Data when collected in original form is called “raw data”.
• For example:
Frequency Distribution
• The researches organizes the raw data by using frequency distribution.
• The frequency is the number of values in a specific class of data.
• A frequency distribution is the organizing of raw data in table form, using classes and frequencies.

Frequency Distribution Cont.
• For the first data set, a frequency distribution is shown as follow:
Types of Frequency Distribution
• There are three basic types of frequency distribution:
• Categorical
• Ungrouped
• Grouped

Categorical Frequency Distribution
• The categorical frequency distribution is used for data that can be placed in specific categories, such as nominal or ordinal data.
• For example, data such as political affiliations, religion affiliations, or major field of study would use categorical frequency distribution.

Example
• The blood type of different students:
Ungrouped Frequency Distribution
• When the range of data is small, the data must be grouped into classes that are not more than one unit in width.

Example
• The range in the example is R=highest value – lowest value : 11 – 4 = 7
• Since the range is small classes consisting of single data value can be used.
Grouped Frequency Distribution
• When the range of the data is large, the data must be grouped into classes that are more than one unit in width.

Example Cont.
• In this distribution, the values 1 and 3 of the first class are called “class limits”.
• 1 is the “lower class limit” and 3 is the “upper class limit.”
Histogram
• The histogram is a graph that displays the data by using vertical bars of various heights to represent the frequencies.

Histogram in Excel (Steps)
• Open the tools menu, choose the data analysis command and chose histogram from the analysis tools list box.
• Input range: enter the reference for the range of cells containing the data.
• Bin range: enter the reference of cells containing the values that separate the intervals, including the labels. (They must be in ascending order).
Steps Continued
• Labels: check this box to indicate that labels have been included in the references for the input range and bin range.
• Out put range: enter the reference for the cell you want out put to appear.
• Chart output: check this option to obtain a histogram chart in addition to the frequency distribution table on the worksheet.

### Create a histogram for the following data:5, 6, 4, 7, 5, 9, 11, 12, 4, 5, 6, 7, 9, 19

Do this in Excel

Cumulative Frequency
• The cumulative frequency is the sum of the frequencies accumulated up to the upper boundary of a class in the distribution.
• They are used to visually represent how many values are below a certain upper class boundary.