NCERT Solutions for Class 10 Maths Chapter 13 Statistics Ex 13.2

Exercise 13.2

1. The following table shows the ages of the patients admitted in a hospital during a year:

Find the mode and the mean of the data given above. Compare and interpret the two measures of central tendency.

Ans: The mean can be found as given below:

$\bar{X}=a+\left(\frac{\sum f_i{u}_i}{\sum f_i}\right)$

Suppose the assured mean $\left(a\right)$ of the data is $$30$$.

Class mark $$\left(x_i\right)$$ for each interval is calculated as follows:

$$x_i=\frac{\text{Upper class limit+Lower class limit}}{2}$$

$$d_i,$$$$u_i,$$and $$f_i{u}_i$$ can be evaluated as follows:

It can be observed that from the above table

$$\sum f_i=80$$ 

$\sum f_i{d}_i=430$ 

Substituting the value of $$u_i,$$ and $$f_i{u}_i$$ in the formula of mean we get:

The required mean:

$\bar{X}=a+\left(\frac{\sum f_i{u}_i}{\sum f_i}\right)$ 

$\bar{X}=30+\left(\frac{430}{80}\right)$

$\bar{X}=30+5.375$

$\bar{X}=35.38$

Hence, the mean of this data is $35.38$. It demonstrates that the average age of a patient admitted to hospital was $35.38$years.

Mode can be calculated as,

$M=l+\left(\frac{f_1-f_0}{2f_1-f_0-f_2}\right)\times h$

Where

$$l=$$ Lower limit of modal class

${\text{f}}_1=$ Frequency of modal class

$$f_0=$$ Frequency of class preceding the modal class

$$f_2=$$ Frequency of class succeeding the modal class

$$h=$$Class size

It can be noticed that the maximum class frequency is $$23$$  belonging to class interval$$35-45$$ .

Modal class $$=35-45$$

The values of unknowns is given as below as per given data:

$$l=35$$ 

$$f_1=23$$ 

$$h=15-5=10$$ 

$$f_0=21$$ 

$$f_2=14$$ 

Substituting these values in the formula of mode we get:

$M=l+\left(\frac{f_1-f_0}{2f_1-f_0-f_2}\right)\times h$

$M=35+\left(\frac{23-21}{2(23)-21-14}\right)\times 10$

$M=35+\left[\frac{2}{46-35}\right]\times 10$

$M=35+\frac{20}{11}$

$\text{M=35+1}\text{.81}$

$\text{M=36}\text{.8}$

Hence, the Mode of the data is $36.8$. It demonstrates that the age of maximum number of patients admitted in hospital was $36.8$years.

2. The following data gives the information on the observed lifetimes (in hours) of $$\mathbf{225}$$ electrical components:

Determine the modal lifetimes of the components.

Ans: Mode can be calculated as,

$M=l+\left(\frac{f_1-f_0}{2f_1-f_0-f_2}\right)\times h$

Where

$$l=$$ Lower limit of modal class

${\text{f}}_1=$ Frequency of modal class

$$f_0=$$ Frequency of class preceding the modal class

$$f_2=$$ Frequency of class succeeding the modal class

$$h=$$Class size

From the data given above, it can be noticed that the maximum class

frequency is$$61$$ belongs to class interval $$60-80$$.

Therefore, Modal class $$=60-80$$ 

The values of unknowns are given as below as per given data:

$$l=\text{60}$$ 

$$f_1=61$$ 

$$h=20$$ 

$$f_0=52$$ 

$$f_2=38$$ 

Substituting these values in the formula of mode we get:

$M=l+\left(\frac{f_1-f_0}{2f_1-f_0-f_2}\right)\times h$

$M=60+\left(\frac{61-52}{2(61)-52-38}\right)\times 20$

$M=60+\left[\frac{9}{122-90}\right]\times 20$

$M=360+\left(\frac{9\times 20}{32}\right)$

 $M=60+\frac{90}{16}=60+5.625$

$M=65.625$

Hence, the modal lifetime of electrical components is $$65.625$$ hours.

3. The following data gives the distribution of total monthly household expenditure of  $$\mathbf{200}$$  families of a village. Find the modal monthly expenditure of the families. Also, find the mean monthly expenditure.

Ans: For mode

Mode can be calculated as,

$M=l+\left(\frac{f_1-f_0}{2f_1-f_0-f_2}\right)\times h$

Where

$$l=$$ Lower limit of modal class

${\text{f}}_1=$ Frequency of modal class

$$f_0=$$ Frequency of class preceding the modal class

$$f_2=$$ Frequency of class succeeding the modal class

$$h=$$Class size

It can be observed from the given data that the maximum class frequency is$$40$$ ,

Belongs to $$1500-2000$$ intervals.

Therefore, modal class $$=1500-2000$$ 

The values of unknowns are given as below as per given data:

$$l=1500$$ 

$$f_1=40$$ 

$$f_0=24$$ 

$$f_2=33$$ 

$$h=500$$ 

Substituting these values in the formula of mode we get:

$M=l+\left(\frac{f_1-f_0}{2f_1-f_0-f_2}\right)\times h$

$M=1500+\left(\frac{40-24}{2(40)-24-33}\right)\times 500$

$M=1500+\left[\frac{16}{80-57}\right]\times 500$

$M=1500+\frac{8000}{23}$

$M=1500+347.826$

$M=1847.826$

$M\approx 1847.83$

Therefore, modal monthly expenditure was Rs $$1847.83$$ .

For mean,

The mean can be found as given below:

$\bar{X}=a+\left(\frac{\sum f_i{u}_i}{\sum f_i}\right)h$

Suppose the assured mean $\left(a\right)$ of the data is $$2750$$.

Class mark $$\left(x_i\right)$$ for each interval is calculated as follows:

$$\text{Class mark}=\frac{\text{Upper class limit+Lower class limit}}{2}$$ 

Class size ($$h$$) of this data is:

$h=1500-1000$

$h=500$

$$d_i,$$$$u_i,$$and $$f_i{u}_i$$ can be evaluated as follows:

It can be observed from the above table

$$\sum f_i=200$$ 

$\sum f_i{u}_i=-35$ 

Substituting $$u_i,$$and $$f_i{u}_i$$ in the formula of mean 

The required mean:

$\bar{X}=a+\left(\frac{\sum f_i{u}_i}{\sum f_i}\right)\times h$ 

$\bar{X}=2750+\left(\frac{-35}{200}\right)\times (500)$ 

$\bar{X}=2750-87.5$

$\bar{X}=2662.5$

Hence, the mean monthly expenditure is Rs$2662.5$ .

4. The following distribution gives the state-wise teacher-student ratio in higher secondary schools of India. Find the mode and mean of this data. Interpret the two Measures.

Ans: For mode

Mode can be calculated as,

$M=l+\left(\frac{f_1-f_0}{2f_1-f_0-f_2}\right)\times h$

Where

$$l=$$ Lower limit of modal class

${\text{f}}_1=$ Frequency of modal class

$$f_0=$$ Frequency of class preceding the modal class

$$f_2=$$ Frequency of class succeeding the modal class

$$h=$$Class size

It can be observed from the given data that the maximum class frequency is $$10$$ which belongs to class interval$$30-35$$ . 

Therefore, modal class $$=30-35$$ 

$$h=5$$ 

$$l=30$$ 

$$f_1=10$$ 

$$f_0=9$$ 

$$f_2=3$$ 

Substituting these values in the formula of mode we get:

$M=l+\left(\frac{f_1-f_0}{2f_1-f_0-f_2}\right)\times h$

$M=30+\left(\frac{10-9}{2(10)-9-3}\right)\times 5$

$M=30+\left(\frac{1}{20-12}\right)\times 5$

$M=30.6$

Hence, the mode of the given data is $30.6$. It demonstrates that most of the states/U.T have a teacher-student ratio of $30.6$ .

For mean,

The mean can be found as given below:

$\bar{X}=a+\left(\frac{\sum f_i{u}_i}{\sum f_i}\right)h$

Suppose the assured mean $\left(a\right)$ of the data is $$32.5$$.

Class mark $$\left(x_i\right)$$ for each interval is calculated as follows:

$$\text{Class mark}=\frac{\text{Upper class limit+Lower class limit}}{2}$$ 

Class size ($$h$$) of this data is:

  $h=20-15$

$h=5$ 

$$d_i,u_i,and{f}_i{u}_i$$ can be calculated as follows:

It can be observed from the above table

$$\sum f_i=35$$ 

$\sum f_i{u}_i=-23$ 

Substituting $$u_i,$$and $$f_i{u}_i$$ in the formula of mean 

The required mean

$\bar{X}=a+\left(\frac{\sum f_i{u}_i}{\sum f_i}\right)\times h$

$\bar{X}=32.5+\left(\frac{-23}{35}\right)\times 5$

$\bar{X}=32.5-\frac{23}{7}$

$\bar{X}=29.22$

Hence, the mean of the data is $29.2$ .

It demonstrates that the average teacher−student ratio was $29.2$.

5. The given distribution shows the number of runs scored by some top batsmen of the world in one-day international cricket matches.

Find the mode of the data.

Ans: Mode can be calculated as

$M=l+\left(\frac{f_1-f_0}{2f_1-f_0-f_2}\right)\times h$

Where

$$l=$$ Lower limit of modal class

${\text{f}}_1=$ Frequency of modal class

$$f_0=$$ Frequency of class preceding the modal class

$$f_2=$$ Frequency of class succeeding the modal class

$$h=$$Class size

From the given data, it can be observed that the maximum class frequency is $18$ 

Belongs to class interval $$4000-5000$$.

Therefore, modal class = $$4000-5000$$

$$l=4000$$ 

$$f_1=18$$ 

$$f_0=4$$ 

$$f_2=9$$ 

$$h=1000$$ 

Substituting these values in the formula of mode we get:

$M=l+\left(\frac{f_1-f_0}{2f_1-f_0-f_2}\right)\times h$

$M=4000+\left(\frac{18-4}{2(18)-4-9}\right)\times 1000$

$M=4000+\left(\frac{14000}{23}\right)$

$M=4608.695$

Hence, the mode of the given data is $$4608.7$$ runs.

6. A student noted the number of cars passing through a spot on a road for $$\mathbf{100}$$  periods each of $$\mathbf{3}$$  minutes and summarised it in the table given below. Find the mode of the data:

Ans: Mode can be calculated as

$M=l+\left(\frac{f_1-f_0}{2f_1-f_0-f_2}\right)\times h$

Where

$$l=$$ Lower limit of modal class

${\text{f}}_1=$ Frequency of modal class

$$f_0=$$ Frequency of class preceding the modal class

$$f_2=$$ Frequency of class succeeding the modal class

$$h=$$Class size

From the given data, it can be observed that the maximum class frequency is $20$,

Belonging to $$40-50$$ class intervals.

Therefore, modal class = $$40-50$$

$$l=40$$ 

$$f_1=20$$ 

$$f_0=12$$ 

$$f_2=11$$ 

$$h=10$$ 

Substituting these values in the formula of mode we get:

$M=l+\left(\frac{f_1-f_0}{2f_1-f_0-f_2}\right)\times h$

$M=40+\left(\frac{20-12}{2(20)-12-11}\right)\times 10$

$M=40+\left(\frac{80}{40-23}\right)$

$M=44.7$

Hence, the mode of this data is $44.7$ cars.

Conclusion

Vedantu's NCERT Solutions for Class 10 Maths Chapter 13 Exercise 13.2 - Statistics explains how to calculate the mode for grouped data. It is important to focus on knowing the formula and correctly understanding frequency distribution tables. This practice is necessary for improving your data analysis qualities and knowing statistical metrics. By carefully practising these solutions, you will improve your understanding of statistics, which will help you with your exams and further studies.

Class 10 Maths Chapter 13: Exercises Breakdown

CBSE Class 10 Maths Chapter 13 Other Study Materials

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