Two Major Areas of Statistics

There are several tools in statistics like graphs, correlation, analysis of variance, and various mean separation tests. Their specific usage depends upon the nature of the study. Yet, whatever tool or method is used, they all belong to any of the two broad areas of statistics.

The first area is what we call as Descriptive Statistics. It comprises those methods concerned with collecting and describing a set of numerical data so as to yield meaningful inference. This statistics provides information only about the collected data and in no way draws inferences. This can either be graphical or computational like construction of tables, charts, graphs, and other relevant computations. It may also include the study of relationships between and among variables.

The second area of statistics is the Inferential Statistics. If descriptive statistics is concerned only on presentation of data, inferential statistics comprises those methods concerned with the analysis of a subset of data leading to predictions or inferences about the entire set of data. It involves all the techniques by which decisions about a statistical population are made based only on a sample having been observed or a judgment having been obtained. It is concerned more with generalizing information or making inference about the population. Considered as the central function of modern statistics, inferential statistics is concerned with two types of problems: (a) estimation of population parameters, and (b) tests of hypothesis.

Example:

Height of Crops as Affected by Different Nitrogen Level (in inches)

Level 1:            3.45     2.86     3.12     2.95     3.05                 Mean – 3.086
Level 2:            4.66     5.54     4.75     5.33     5.24                 Mean – 5.104
Level 3:            5.32     7.65     6.87     7.41     7.36                 Mean – 6.922

Descriptive Statistics:
  • The shortest plant has a height of 2.86 inches while the tallest is 7.65 inches.
  • Plants in Level 1 have a mean height of 3.086 inches, while Levels 2 and 3 produce mean heights of 5.104 and 6.922 inches, respectively.
  • Level 1 nitrogen produced the shortest plants, while level 3 the tallest.
  • Plants in the experiment have a grand mean of 5.037 inches.
  • Chart of Mean Height (in inches)
 
Inferential Statistics:
  • Based on the results, the height of plants increases as the level of nitrogen application increases.
  • Plant height in Level 1 is statistically different from Level 2 and 3. However, difference in Levels 2 and 3 is not significantly different from each other.
  • There is a strong correlation between the level of nitrogen application and plant height.

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