2016-2017 Descriptive Biostatistics

The best way to work with data is to summarize and organize them. 
Numbers that have not been summarized and organized are called raw data.
A descriptive measure is a single number that is used to describe a set of data. 
Descriptive measures include measures of central tendency and measures of dispersion.
Uniqueness: For a given set of data there is one and only one mean.
Simplicity: The mean is easy to calculate.
Affected by extreme values : The mean is influenced by each value. Therefore, extreme values can distort the mean.
The median is the value that divides the set of data into two equal parts. The number of values equal to or greater than median equals the number of values less than or equal the median.
Properties of the median:
1.Uniqueness: There is only one median for each set of data.2.Simplicity: It is easy to calculate.3.Effect of extreme values: The median is not as drastically affected by extreme values as is the mean.
1.  Arrange the data in order of increasing value in a sorted list.
2.  Find the median.  
a.  Odd number of values (n is odd).
Median = X (n+1/2).
b.  Even number of values (n is even).      
Median = average of the two values in the middle.