1. Chapter 1 Statistics by Mohamed ELhusseiny
Statistic Course
Chapter 1
Statistics by
Mohamed ELhusseiny

2. Introduction
Statistics is the sciences of converting data to information.
Statistics is a group of methods that are used to collect, analyze, present, and interpret data and make decisions
Types of statistics
Generally speaking there are to types of statistics
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3. Introduction Generally speaking there are to types of statistics
Descriptive statistics
The type of statistics that is used to organize, summarize and describe the given data
Inferential statistics
The type of statistics that is uses a portion (A sample) of a large group of elements ( A population) to get information about the population instead of using the whole population that could be economically expensive.
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4. Population versus sample
Introduction
inferential statistics
consists of methods that use sample results to help make decisions or predictions about a population.
Population versus sample
A population consists of all elements (individuals, items, or objects) whose characteristics are being studied
A sample of the population is a subset of this population
A population
A sample
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5. Types of Variables and types of data
The variables used by statistics is usually classified based on there types. There are two types of variables
Variables
Discrete
Continuous
Type of Data
(Qualitative)
Type of Data
(Quantitative)
Nominal Data
Ordinal Data
Numerical Data
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6. Types of data
Numerical (Interval) Data: data that are measured, such as, time, age, weight, money, distance, amount of rain,…
Nominal data: data that are used to describe an event, such as gender, blood type, marital status, number of care accidents per year,….
Ordinal data: data that are used to describe an event but in a given order, such as weather condition, course evaluation, Quality of a magazine,…
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7. Graphical techniques for description of data
Type of Data
Numerical Data
Nominal Data
Ordinal Data
Histogram, Ogive, Stem and Leaf, and Box plots
Bar, Pie, and Line Charts
Box plots
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8. Graphical techniques for description of data
Bar Charts
Blood Type
Frequency A 50 B
120 AB 80 O
150
total
400
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9. Graphical techniques for description of data
Pie Charts
Blood Type
Frequency A 50 B
120 AB 80 O
150
total
400
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10. Graphical techniques for description of data
Bar Charts
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11. Graphical techniques for description of data
Pie Charts
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12. Graphical techniques for description of data
Pie Chart
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13. Graphical techniques for description of data
Histogram
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14. Histogram
Question:
How do I choose the number of classes and the width of the classes to be used in constructing a frequency distribution?
Answer: Although this choice is arbitrary and no hard and fast rules can be given, here are a few useful guidelines:
The classes must be nonoverlapping, so that each measurement falls into exactly one class. Therefore, choose the classes so that no measurement falls on a class boundary.
The number of classes can be chosen by Struges’ formula
Number of classes = log (n)
Where n is the size of the data
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15. Graphical techniques for description of data
Choose the number of classes to be used as a number between 5 and 20, with smaller numbers of classes being chosen for smaller data sets. The approximate width of each class is given by the following:
Choose the actual class width to be a value close to the approximate width that is convenient to work with. Avoid awkward fractional values.
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16. Histogram
Example
The weights in pounds of a group of workers are as follows:
Construct a frequency distribution for these data.
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17. Histogram Steps to construct the Histogram
1- choosing the No. of classes: Number of classes = log (n)
= log (25) = 5.6 = 5 or 6
2- Approximate Class width = (188 – 140 ) / 5 = 48/5 = approxi. 10
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18. Histogram Steps to construct the Histogram
1- choosing the No. of classes: Number of classes = log (n)
= log (25) = 5.6 = 5 or 6
2- Approximate Class width = (188 – 140 ) / 5 = 48/5 = approxi. 10
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19. Histogram
Shapes of Histogram
1- Symmetry
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20. Histogram Shapes of Histogram 1- Skewness Positively Skewed Histogram
Negatively Skewed Histogram
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21. Histogram Shapes of Histogram 1- Number of Modal Classes
Unimodal Histograms
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22. Histogram Shapes of Histogram 1- Number of Modal Classes
Bimodal Histograms
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23. Thank you
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