Q1. What do you understand by the word “statistics” in:
(a)Singular form (B) Plural form
Solution 1:
The word statistics is used in both its singular and plural senses.
(a) In singular sense, statistics may be defined as the science of collection, presentation, analysis and interpretation of numerical data.
(b) In plural sense, statistics means numerical facts or observations collected with definite purpose.
For example: Income and expenditure of persons in a particular locality,number of persons in a particular locality ,number of males and females in a particular town are statistics.
Q2.Describe some fundamental characteristics of statistics.
Solution 2:
Fundamental characteristics of statistics
(1) A single observation does not form statistics. Statistics are a sum total of observations.
(2) Statistics are expressed quantitatively not qualitatively.
(3) Statistics are collected with definite purpose.
(4) Statistics in an experiment are comparable and can be classified into groups.
Q3. What are (1) primary data (2) secondary data? Which of the two—the primary or the secondary data—is more reliable and why?
Solution 3:
The word data means information statistical data and are of two types:
(1) Primary data
When an investigator collects data himself with a definite plan or design in hs or her mind is called primary data.
(2)Secondary data
Data which are not originally collected rather obtained from published or unpublished sources are called secondary data.
Secondary data are collected by an individual or an institution for some purpose and are used by someone else in another context.
Primary data are reliable and relevant because they are original in character and are collected by some individuals or by research bodies.
Q4. Why do we group data?
Solution 4: The data obtained in original form are called raw data .Raw data does not give any useful information and is rather confusing to mind. Data is grouped so that it becomes understandable and can be interpreted. According to various characteristics groups are formed by us. After grouping the data, we are in position to make calculations of certain values which will help us in describing and analyzing the data.
Q5. Explain the meaning of the following terms:
(1)Variate
(2)Classintegral
(3)Classsize
(4)Classmark
(5) Frequency
(6)Class limits
(7)True class limits
Solution 5:
(1) Variate
Any character that can vary from one individual to another is called variate.
(2)Class interval
In the data each group into which raw data is considered is called a classinterval.
(3)Classsize
The difference between the true upper limit and lower limit is called the class size of that class size.
(4)Classmark
The middle value of the class is called as the class mark.
Class mark =
(5)Frequency
The number of observations corresponding to class is called its frequency.
(6)Class limits
Each class is bounded by two figures ,called the class limits .The figures on the left side of the classes are called lower limits while figures on the right side are called upper limits.
(7)True class limits
If classes are inclusive.Eg:1519,2024,2529….
Then, true lower limit of class = upper limit of class0.5
Eg: True limits of the class is 1519 are 14.5 and 19.5
But if classes are exclusive like 1020,2030,3040…
Here class limits and true class limits are the same.
Q6.The ages of ten students of a group are given below.The ages have been recorded in years and months:
86,90,84,93,78,811,87,92,710,88
(i)What is the lowest age?
(ii)What is the highest age?
(iii)Determine the range?
Solution 6:
The ages of ten students of a group are given below
86,90,84,93,78,811,87,92,710,88.
(1)Lowest age is 7 years 8months
(2)Highest age is 9 years,3 months
(3)Range = Highest agelowest age = 9 year,3 months,7 years,8 months = 1 year 7 months
Q7.The monthly pocket money of six friends is given below:
Rs 45,Rs 30, Rs 40, Rs 25, Rs 45.
(i)What is the lowest pocket money?
(ii)What is the highest pocket money?
(iii)What is the range?
(iv)Arrange the amounts of pocket money in ascending order
Solution 7:
The monthly pocket money of six friends is given below:
Rs45,Rs 30, Rs 40, Rs 25, Rs 45.
(1) Highest pocket money = Rs 50
(2) Lowest pocket money = Rs 25
(3) Range = 5025 = 25
(4) The amounts of pocket money in an ascending order is: Rs 25,Rs 30, Rs 40, Rs 45, Rs 45,Rs 50.
Q8.Write the class size in each of the following:
1)04, 59, 1014
(2) 1019, 2029, 3039
(3) 100120, 120140, 160180
(4) 00.25, 0.2500.50, 0.500.75
(5) 55.01, 5.015.02, 5.025.03.
Solution 8:
(1) 04 ,59, 1014
True class limits are 0.54.5,4.59.5,9.514.5
Therefore class size = 14.59.5 = 5
(2) 1019 , 2029 , 3039
True class limitsà 19.519.5,19.529.5,29.529.5
Class size = 39.529.5 = 10
(3) 100120 , 120140, 160180
Here the class limits and true class limits are the same
Therefore class size = 120100 = 20
(4) 00.25,0.2500.50,0.500.75
Here the class limits and true class limits are the same
Therefore class size = 0.250 = 0.25
(5) 55.01,5.015.02,5.025.03.
Here the class limits and true class limits are the same
Therefore class size = 5.015.0 = 0.01.
Q9. The final marks in mathematics of 30 students are as follows:
53,61,48,60,78,68,55,100,67,0,75,88,77,37,84,58,60,48,62,56,44,58,52,64,98,59,70,39,50,60.
(i)Arrange these marks in ascending order,30 to 39 one group,40 to 49 second group etc.
Now answer the following:
(ii)What is the lowest score?
(iii)What is the highest score?
(iv)What is the range?
(v)If 40 is the pass mark how many failed?
(vi)How many have scored 75 or more?
(vii)Which observations between 50 and 60 have not actually appeared?
(viii) How many have scored less than 50?
Solution 9:
The final marks in mathematics of 30 students are as follows:
53,61,48,60,78,68,55,100,67,0,75,88,77,37,84,58,60,48,62,56,44,58,52,64,98,59,70,39,50,60.
(1)
Group  Class  Observations 
I  3039  37,39 
II  4049  44,48,48 
III  5059  50,52,53,55,56,58,58,59 
IV  6069  60,60,60,61,62,64,67,68 
V  7079  70,55,77,78 
VI  8089  84,88 
VII  9099  90,98 
VIII  100109  100 
(2) Highest score = 100
(3)Lowest score = 37
(4)Range = 10037 = 63
(5)If 40 is the passing marks,2 students have failed
(6) 8 students have scored 75 or more
(7)Observation 51, 54, 57 between 50 and 60 has not actually appeared.
(8) 5 students have scored less than 50
Q10. The weights of new born babies are as follows: 2.3,2.2,2.1,2.7,2.6,2.5,3.0,2.8,2.8,2.9,3.1,2.5,2.8,2.7,2.9,2.4.
(i)Rearrange the weights in descending order.
(ii)What is the highest weight?
(iii)What is the lowest weight?
(iv)Determine the range?
(v)How many babies were born on that day?
(vi)How many babies weigh below 2.5 Kg?
(vii) How many babies weigh more than 2.8 Kg?
(viii)How many babies weigh 2.8 Kg?
Solution 10:
The weights of new born babies(in kg) are as follows
2.3,2.2,2.1,2.7,2.6,2.5,3.0,2.8,2.8,2.9,3.1,2.5,2.8,2.7,2.9,2.4.
(1) The weights in descending order
3.1,3.0,2.9,2.9,2.8,2.8,2.7,2.7,2.6,2.5,2.5,2.4,2.3,2.2,2.1.
(2) The highest weight = 3.1 Kg
(3) The lowest weight = 2.1 Kg
(4) Range = 3.12.1 = 1.0 Kg
(5) 15 babies were born on that particular day.
(6)4 babies weight below 2.5 Kg.
(7) Weight more than 2.8 Kg are 4 babies.
(8) Weightà2 babies
Q11. The number of runs scored by a cricket player in 25 innings is as follows : 26,35,94,48,82,105,53,0,39,42,71,0,64,15,34,15,34,6,71,0,64,15,34,15,34,67,0,42,124, 84,54,48,139,64,47
(i)Rearrange these runs in ascending order.
(ii)Determine the player, is highest score.
(iii)How many times did the player not score a run?
(iv)How many centuries did he score?
(v)How many times did he score more than 50 runs?
Solution 11:
The numbers of runs scored by a player in 25 innings are
26,35,94,48,82,105,53,0,39,42,71,0,64,15,34,15,34,6,71,0,64,15,34,15,34,67,0,42,124,84,54,48,139,64,47.
(i) Runs in an ascending order are
0,0,0,0,6,15,15,15,15,26,34,34,34,34,35,39,42,42,47,48,48,53,54,64,64,64,67,71,71,82,90,124,139.
(ii) The highest number = 139
(iii) The player did not score any runs 3 times
(iv) He scored 3 centuries.
(v) He scored more than 50 runs 12 times.
Q12. The class size of distribution is 25 and the first classinterval is 200224. There are seven classintervals.
(i)Write the classintervals.
(ii)Write the class marks of each interval.
Solution 12:
Given
Class size = 25
First class interval = 200224
(i)Seven class interval are:
200240,225249,250274,275299,300324,325349,350374.
(ii) Class mark 200224 =
= 212
Class mark 225249 =
= 237
Class mark 250274 =
= 287
Class mark 300324 =
= 312
Class mark 325349 =
= 337
Class mark 350374 =
= 362
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