STD IX – STATISTICS – ARCHIMEDES

STATISTICS

Data

A collection of information is called data.

Primary data: Primary data is that which is collected by the investigator himself through personal observations with a definite plan or design in mind.

For example, the data collected by a teacher on the performance of students in mathematics. Primary data is reliable and relevant.

Secondary data: Secondary data is that which has been collected previously by someone other than the investigator for some specific purpose.

For example, government reports

Raw Data: Raw data is the data that is simply collected and written down haphazardly, i.e., not in an arranged manner. This kind of data rises difficulties in computing, analyzing, and interpreting it.

Arrayed Data: Arrayed data (also known as grouped data) is that data that has been classified in either a serial or alphabetical order or in an ascending or descending order. This kind of data makes it very easy to compute, analyze, and interpret.

MEAN AND MEDIAN

Mean

Measures of central tendency are a key way to discuss and communicate with graphs. The term central tendency refers to the middle, or typical, value of a set of data, which is most measured by using the three m’s: mean, median, and mode. The mean, median, and mode are known as the measures of central tendency.

Under different conditions, some measures of central tendency become more appropriate to use than others. In the following sections, we will look at the mean and median, and learn how to calculate them.

Median

A median is a measure of central tendency which gives the value of the middle-most observation in the data Median is the middle score when the data is arranged in ascending or descending order

There will be equal number of items above and below median 50% of total frequency is below and above it