# Statistics

## Class 9 NCERT Maths

### NCERT

1   Give five examples of data that you can collect from day to day life.

##### Solution :

In our day to day life, we can collect the following data.$\\$ 1. Number of females per $1000$ males in various states of our country$\\$ 2. Weights of students of our class$\\$ 3. Production of wheat in the last $5$ years in our country$\\$ 4. Number of plants in our locality$\\$ 5. Rainfall in our city in the last $12$ months.

2   Classify the data in $Q1$ above as primary or secondary data.

##### Solution :

The given data is very large. So, we construct a group frequency of class size $5$.$\\$ Therefore the class interval will be $0-5,5-10,10-15$ and so on.$\\$ The data is represented in table as:$\\$ The classes in the table are not overlapping. Also, $36$ out of $40$ Engineers have their houses below $20km$ distance.

5   The relative humidity (in %) of a certain city for a month of 30 days was as follows:$\\$ $98.1 \ 98.6 \ 99.2 \ 90.3 \ 86.5 \ 95.3 \ 92.9 \ 96.3 \ 94.2 \ 95.1$$\\ 89.2 \ 92.3 \ 97.1 \ 93.5 \ 92.7 \ 95.1 \ 97.2 \ 93.3 \ 95.2 \ 97.3$$\\$ $96.2 \ 92.1 \ 84.9 \ 90.2 \ 95.7 \ 98.3 \ 97.3 \ 96.1 \ 92.1 \ 89$$\\ (i) Construct a grouped frequency distribution table with classes 84-86, 86-88$$\\$ (ii) Which month or season do you think this data is about?$\\$ (iii) What is the range of this data?

##### Solution :

(i) A grouped frequency distribution table of class size $2$ has to be constructed. The class intervals will be $84-86, 86-88,$ and $88-90, ...$ By observing the data given above, the required table can be constructed as follows:$\\$ (ii) It can be observed that the relative humidity is high. Therefore, the data is about a month of rainy season.$\\$ (iii) Range of data = Maximum value - Minimum value$\\$ $= 99.2 - 84.9 = 14.3$