Page 261 - ICSE Math 7

AT A GLANCE

¾ A collection of numerical facts about an information is called data. Each numerical figure in a
data is called an observation.

¾ Series of individual observations is called raw data.
¾ The number of times a variable occurs in a data is called its frequency. Raw data can be converted
into frequency distribution table also known as discrete series.
¾ Collection, recording and presentation of data help us to organize our information and draw
inferences from them.
¾ Arithmetic mean is one of the central tendencies and is obtained as follows:

Mean = x 1 + x2 + ... + xn (for raw data)
n
f x 1 + f x 2 + ... + f x n
Mean = 1 2 n (for grouped data)
f 1 + f 2 + ... + f n
¾ Median is the middlemost value of the data and it divides the data into two equal halves. Median
is also one of the central tendencies. In arranged data:
n + 1
Median = th observation, if n is odd
2
n n
Median = Average of th and + 1 th observation, if n is even
2 2
¾ Mode is the value of the observation which occurs the maximum number of times in the data.
This central tendency is helpful in deciding about the size of the item to be stocked.

¾ Arithmetic mean, median and mode are representative value of the data. But their selection
should be done judiciously depending upon the nature of the data and the purpose for which the
average is required.

¾ A bar graph is pictorial representation of data using bars of equal width with uniform spaces
between them.

¾ Multiple bar graphs help us to compare two or more collections at a glance.

MENTAL MATHS

1. Choose the correct answer.

(a) Which of the following is not a central tendency?
(i) Mean (ii) Range (iii) Median (iv) Mode
(b) Mode is the value of the data ___________.

(i) having maximum value
(ii) whose position is in the middle

(iii) occurring maximum number of times
(iv) occurring minimum number of times

(c) What is the value of mode for the data 3, 4, 1, 4, 3, 6, 0, 3, 3, 2, 6, 2, 6, 1?
(i) 3 (ii) 6 (iii) 4 (iv) 2

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