Elementary Statistics and Computer Application

Population (Universe)

• Population means aggregate of all possible units. It need not be human population. It may be population of plants, population of insects, population of fruits, etc.
 
Finite population
When the number of observation can be counted and is definite, it is known as finite population

• No. of plants in a plot.
• No. of farmers in a village.
• All the fields under a specified crop.

Infinite population
When the number of units in a population is innumerably large, that we cannot count all of them, it is known as infinite population.

• The plant population in a region
• The population of insects in a region

Frame

• A list of all units of a population is known as frame.

Parameter

• A summary measure that describes any given characteristic of the population is known as parameter. Population are described in terms of certain measures like mean, standard deviation etc. These measures of the population are called parameter and are usually denoted by Greek letters. For example, population mean is denoted by μ , standard deviation by σ and variance by σ² .

Sample
A portion or small number of unit of the total population is known as sample.

• All the farmers in a village(population) and a few farmers(sample)
• All plants in a plot is a population of plants.
• A small number of plants selected out of that population is a sample of plants.

Statistic

• A summary measure that describes the characteristic of the sample is known as statisitic. Thus sample mean, sample standard deviation etc is statistic. The statistic is usually denoted by roman letter.
• -sample mean
• s – standard deviation
• The statistic is a random variable because it varies from sample to sample.