“Today’s weather - warm and sunny throughout the day, heavy
rain expected in the evening,” said a stylish newsreader on
television.

“You better carry your umbrella, Sankhya,” cautioned Amma.

“I think I’ll cut the grass in the backyard tomorrow,” said
Father.

“I’m going to make paper boats of all kinds. Yippee!” danced
Ganith.

Data

Data is nothing but information.

Actually, the singular of data is datum. Funny word!

We use data to form opinions, to make arrangements, to organise
matters and to inform others.

Sankhya and her family used the data from the news on television
to organise their time. Mathematical data is very useful too.

We use mathematical data, also called statistics, in many ways.

*Different forms of data:*

On television.

in a Newspaper

Charts and Statistics.

Sankhya likes writing tests. Her marks indicate
whether she has learnt her lessons well.
When she gets ‘above average’ marks
she feels happy.

But what does average mean?

Let’s see. These are the marks out of 100 that Sankhya and her
19 classmates got in the last mathematics examination.

74, 65, 35, 57, 59, 53, 44, 88, 97, 33, 86, 88, 88, 45, 61, 79, 88,
56, 57, 67.

Let us add all these marks.

74+65+35+57+59+53+44+88+97+33+86+88+88+45+61+79+88+56+57+67=1320
74
65
35
57
59
53
44
88
97
33
86
88
88
45
61
79
88
56
57
67
1320
.

The number we get when we divide the sum by the number of
students is called Arithmetic Mean, or average.

1320 divided by 20=66.

Mean score in Sankhya’s class in Mathematics is 66. Anyone who
gets around this has scored average marks. Students who get
higher marks than the mean have scored above average marks.
Students who score much less than the mean need to do much
better in the next examination!

Mode

What have most students in Sankhya's class scored?

Let’s put the marks in ascending order, that is, from the lowest
to the highest.

Mode is the figure that appears most often in the list.
In the list 88 is the Mode.

Median

Median is the number that appears in the middle of the list after
you have put it in descending or ascending order.

In a group of 20 numbers, the 10th and 11th numbers are in the
middle. Median is the value between these two numbers that is
between 61 and 65.

Median in this example is 63. (
61+652=1262=63
61
65
2
126
2
63
)