Page 295 - Start Up Mathematics_7

5. Arithmetic mean is one of the central tendencies and is obtained as follows:

Mean = x 1 + x2 + ... + xn (for raw data)
n

1
n
2
Mean = f x 1 + f x 2 + ... + f x n (for discrete series)
f 1 + f 2 + ... + f n
6. 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
7. 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.
8. 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.

9. A bar graph is pictorial representation of data using bars of equal width with uniform spaces
between them.
10. Multiple bar graphs help us to compare two or more collections at a glance.

Review Exercises

Multiple ChoiCe Questions

1. Which of the following is not a central tendency?
(a) Mean (b) Range (c) Median (d) Mode

2. Mode is the value of the data:
(a) having maximum value (b) whose position is in the middle
(c) occurring maximum number of times (d) occurring minimum number of times

3. The median of 3, 2, 1, 2, 1, 5, 2 is:
(a) 1 (b) 2 (c) 3 (d) 2.5

4. The mean marks of 5 students is 23. If the marks scored are 20, 21, 23, 18 and x, then x is:
(a) 20 (b) 23 (c) 28 (d) 33

5. The value of mode for the data 3, 4, 1, 4, 3, 6, 0, 3, 3, 2, 6, 2, 6, 1 is:
(a) 3 (b) 6 (c) 4 (d) 2

6. A cricketer scores the following runs in eight innings: 48, 72, 30, 56, 0, 7, 100. The range of
runs scored is:
(a) 30 (b) 56 (c) 93 (d) 100
7. The height of a door needed in a house is appropriately represented by taking the users’:

(a) mean (b) median (c) mode (d) none of these

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