Page 264 - ICSE Math 8

MENTAL MATHS

1. Choose the correct option.
(a) The number of times an observation occurs in a data is called its:
(i) range (ii) frequency (iii) class size (iv) none of them
(b) The class marks of an interval are also known as the:
(i) width of class interval (ii) class size (iii) mid-value of class interval (iv) class limit
(c) The range of the data 6, 12, 9, 15, 8, 5, 14, 7, 6, 3 is:
(i) 13 (ii) 10 (iii) 11 (iv) 12
(d) The inclusive class intervals are also called:
(i) discontinuous class intervals (ii) continuous class intervals
(iii) unequal class intervals (iv) higher class intervals
(e) To convert 1–5, 7–11, 13–17, ... into exclusive class intervals we:
1 1
(i) add to the upper limit and subtract from the lower limit.
2 2
(ii) add 1 to the lower limit and subtract 1 from the upper limit.
1 1
(iii) add to the lower limit and subtract from the upper limit.
2 2
(iv) add 1 to the upper limit and subtract 1 from the lower limit.
(f) Which of the following depends on the numerical value of the data represented in a bar graph?
(i) Height of the rectangle (ii) Length of the rectangle
(iii) Area of the rectangle (iv) All of them
2. Write True or False.
(a) The data which can take only whole number values is called continuous data.
(b) When the class intervals are so arranged that the upper limit of one class is the lower limit of the
next class, it is called exclusive or continuous class interval.
(c) Raw data is already arranged in a meaningful format.
(d) There are two types of class intervals—discrete and continuous.
(e) A bar graph is graphical representation of numerical data in the form of rectangles (or bars) of equal
width and varying heights.
3. Fill in the blanks.
(a) To avoid errors in counting large number of observations, vertical bars or lines called ____________
marks are used to mark the ____________.
(b) The data tabulated in the ____________ class interval style needs to be re-adjusted to ____________
class interval style for easy comprehension and uniform class interval.
(c) The first class interval of any grouped frequency distribution contains the ____________ value and
the last class interval contains the ____________ value of the data.
(d) In a bar graph, bars are drawn either ___________ or ___________ keeping equal space between them.
(e) In a pie chart, the central angle of sector is given by the formula ____________.

PRACTICE TIME

1. Form a discrete frequency distribution for the following data.
10, 14, 14, 18, 10, 21, 21, 18, 10, 14, 18, 14, 21, 27, 18, 21, 27, 27, 22, 10, 10, 18, 22, 14, 10, 18, 21, 21, 27, 18
2. The reading for relative humidity measured (rounded off to the nearest percentage) for 20 days is given
below.
45, 34, 67, 83, 32, 35, 25, 29, 67, 54, 95, 99, 92, 91, 76, 71, 18, 19, 26, 45
Construct a grouped frequency table with equal class interval 10–20, 20–30, ..., etc.

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