BIOSTATISTICS- Introduction, Measure of central tendency

INTRODUCTION:

STATISTICS : is the science of compiling, classifying and tabulating numerical data & expressing the results in a mathematical or graphical form.
BIOSTATISTICS : is that branch of statistics concerned with mathematical facts & data related to biological events.

USES OF STATISTICS:

To assess the state of oral health in the community and to determine the availability and utilization of dental care facilities.
To indicate the basic factors underlying the state of oral health by diagnosing the community and solutions .
To determine success or failure of specific oral health care programs or to evaluate the program action.
To promote health legislation and in creating administrative standards.

MEASURES OF CENTRAL TENDENCY:

A single estimate of a series of data that summarizes the data – the measure of central tendency.

Objective:

PROPERTIES:

Should be easy to understand and compute.
Should be based on each and every item in the series.
Should not be affected by extreme observations.
Should be capable of further statistical computations.
Should have sampling stability.
The most common measures of central tendeny that are used in dental sciences are :

Arithmetic mean – mathematical estimate.
- Simplest measure of central tendency.
- Most commonly used
- Ungrouped data:Mean=Sum of all the observations in the data / Number of observations in the data
- Grouped data:Mean=Sum of all the variables multiplied by the corresponding frequency in the data/ Total frequency
Median – positional estimate:
- Middle value in a distribution such that one half of the units in the distribution have a value smaller than or equal to the median and one half have a value greater than or equal to the median.
- Extreme values in the series
- All the observations are arranged in the order of the magnitude.
- Middle value is selected as the median.
- Most commonly used statistical average.
- Odd number of observations : (n+1)/2.
- Even number of observations: mean of the middle two values is taken as the mean.
Mode – based on frequency:

The mode or the modal value is that value in a series of observations that occurs with the greatest frequency.
When mode is ill defined, it can be calculated using the relation
Mode = 3 median – 2 mean

Mean and standard deviation can be worked out only if data is on Interval/Ratio scale
Median is the most commonly used statistical average.

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