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# Standard deviation

Clinical Instructor em Dubai Corporation for Ambulance Services (DCAS)
8 de Apr de 2017
1 de 11
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### Standard deviation

1. Standard Deviation Presented by: Sultan Sultan AbdelrahmanAl Kilani
2. Overview • Objectives • Definition of Standard Deviation • Merits and demerits of Standard Deviation • The calculation of Standard deviation
3. Objectives At the end of this presentation you should be able to : - Define the standards deviation - List the merit and demerit of obtaining standards deviation - Calculate the variance and standard deviation
4. Standard Deviation - Standard deviation measures the dispersion of data. - It shows the average absolute distance of each point from the mean - The greater the value of standard deviation, the further the data tend to be dispersed from the mean.
5. Merits of Standard Deviation 1- It is the most reliable measure of dispersion 2- It is most widely used measure of dispersion or variability 3- Its computation is based on all the observations.
6. Demerits of Standard Deviation 1- It is relatively difficult to calculate and understand. 2- It cannot be used for comparing the dispersion of two, or more series given in different units. 3- It is affected very much by the extreme values
7. Formula Standard deviation has a symbol (σ) if the data represent a population and (s) if the data represent a sample σ = (𝒙− 𝒙 ) 𝟐 𝒏 s = (𝒙− 𝒙 ) 𝟐 𝒏−𝟏 Population Sample
8. Example: find the standard deviation for a population data: 6, 4, 5, 7, 8
9. σ = (𝒙− 𝒙 ) 𝟐 𝒏 = 𝟏𝟎 𝟓 = 𝟐 = 1.4 (𝒙 − 𝒙) 𝟐𝒙 − 𝒙Xn 06-6=061 44-6=-242 15-6 = -153 17-6 = 174 28-6 = 285 10(𝑥 − 𝑥)2 = Solution:
10. Summary - Standard deviation measure the dispersion of data. - It is the most reliable - The greater the value of standard deviation, the further the data tend to be dispersed from the mean.
11. References Stacey B., Laurel S. (1st edtion). Statistics for Nursing and Allied Health
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