The various

terms related to statistics are discussed using examples.

**Data: **

The collection

of information in the form of numerical figures, regarding different aspects of

life is called **data**. The data

can be about population, birth, death, temperature of place during a week,

marks scored in the class, runs scored in different matches, etc. We need to

analyze this data.

**For Example:**

The following table gives the data regarding the number of students

opting for different activities.

Activities | Dance | Music | Art | Sports |

No. of students | 15 | 25 | 10 | 40 |

**Raw data:**

When some

information is collected randomly and presented, it is called a raw **data**.

**For Example:**

Given below

are the marks (out of 25) obtained by 20 students of class **VII A** in mathematics in a test.

18, 16, 12, 10,

5, 5, 4, 19, 20, 10, 12, 12, 15, 15, 15, 8, 8, 8, 8, 16

**Observation:**

Each entry

collected as a numerical fact in the given data is called an observation.

**Array:**

The raw data

when put in ascending or descending order of magnitude is called an array or

arrayed data.

**For Example:**

The above data

is arranged in ascending order and represented as:

4, 5, 5, 8, 8, 8, 8, 10, 10, 12, 12, 12, 15, 15, 15, 16, 16, 18, 19, 20

**Range:**

The difference between the highest and the lowest value of

the observation is called the range of the data.

*In the above data,*

Highest marks obtained = 20

Lowest marks obtained = 4

Therefore, range = 20 – 4 = 16

**Mean: **

It is calculated by dividing the sum of all the observation by the total number of observations. If x, x_{1}, x_{3}, ……… x_{n} are n observations then

**Arithmetic mean** = (x_{1} + x_{2} + x_{n}, ……………. x_{n})/n = (∑x_{i})/n

[∑ is the Greek letter sigma and is used to denote summation]

**For
Example: **

The heights of 10 girls were measured in

cm and results are as follows:

**142, 149, 136, 148, 129,
140, 148, 145, 150, 133**

(i) What is the height

of the tallest girl?

**Solution:**

The height of the

tallest girl is 150 cm.

(ii) What is the height

of the shortest girl?

**Solution:**

The height of the

shortest girl is 129 cm

(iii) What is the range

of the data?

**Solution:**

Range = 150 cm – 129 cm

= 21 cm

(iv) Find the mean

height.

**Solution:**

The mean height = (142 +

149 + 136 + 148 + 129 + 140 + 148 + 145 + 150 + 133)/10

= 1420/10

= 142 cm

(v) How many girls are

there whose height is less than the mean height?

**Solution:**

There are 4 girls whose

height is less than the mean height, i.e., the girl having heights 136 cm, 129 cm,

133 cm, 140 cm.

The terms related

to statistics are data, raw data, array, range, mean are explained above using

examples.

**● Statistics**

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