Class 9 - Mathematics
Statistics - Exercise 14.4
Top Block 1
Exercise 14.4
Question :1 : The following number of goals was scored by a team in a series of 10 matches:
2, 3, 4, 5, 0, 1, 3, 3, 4, 3
Find the mean, median and mode of these scores.
Answer :
The number of goals scored by the team is
2, 3, 4, 5, 0, 1, 3, 3, 4, 3
Mean of data = Sum of all observations/Total number of observations
= (2 + 3 + 4 + 5 + 0 + 1 + 3 + 3 + 4 + 3)/10
= 28/10
= 2.8 goals
Arranging the number of goals in ascending order,
0, 1, 2, 3, 3, 3, 3, 4, 4, 5
The number of observations is 10, which is an even number. Therefore,
Median = (5th term + 6th term)/2
= (3 + 3)/2
= 6/2
= 3
Mode of data is the observation with the maximum frequency in data.
Therefore, the mode score of data is 3 as it has the maximum frequency as 4 in the data.
Question : 2: In a mathematics test given to 15 students, the following marks (out of 100) are recorded:
41, 39, 48, 52, 46, 62, 54, 40, 96, 52, 98, 40, 42, 52, 60
Find the mean, median and mode of this data.
Answer :
The marks of 15 students in mathematics test are
41, 39, 48, 52, 46, 62, 54, 40, 96, 52, 98, 40, 42, 52, 60
Mean of data = Sum of all observations/Total number of observations
= (41 + 39 + 48 + 52 + 46 + 62 + 54 + 40 + 96 + 52 + 98 + 40 + 42 + 52 + 60)/15
= 822/15
= 54.8
Arranging the scores obtained by 15 students in an ascending order,
39, 40, 40, 41, 42, 46, 48, 52, 52, 52, 54, 60, 62, 96, 98
As the number of observations is 15 which is odd, therefore, the median of data will
be (15+1)th/2 = 16th/2 = 8th observation whether the data is arranged in an ascending or
descending order.
Therefore, median score of data = 52
Mode of data is the observation with the maximum frequency in data. Therefore, mode of this
data is 52 having the highest frequency in data as 3.
Question : 3: The following observations have been arranged in ascending order. If the median of the data is 63, find the value of x.
29, 32, 48, 50, x, x + 2, 72, 78, 84, 95
Answer :
It can be observed that the total number of observations in the given data is 10 (even
number). Therefore, the median of this data will be the mean of 10/2
i.e., 5th and (10/2)+1 i.e., 6th term.
Therefore, median of data = (5th observation + 6th observation)/2
⇒ 63 = (x + x + 2)/2
⇒ 63 * 2 = 2x + 2
⇒ 126 = 2x + 2
⇒ 2x = 126 – 2
⇒ 2x = 124
⇒ x = 124/2
⇒ x = 62
So, the value of x is 62
Question : 4: Find the mode of 14, 25, 14, 28, 18, 17, 18, 14, 23, 22, 14, and 18.
Answer :
Arranging the data in an ascending order,
14, 14, 14, 14, 17, 18, 18, 18, 22, 23, 25, 28
It can be observed that 14 has the highest frequency, i.e. 4, in the given data.
Therefore, mode of the given data is 14.
Question : 5: Find the mean salary of 60 workers of a factory from the following table:
Answer :
Using the table, the mean can be calculated as follows.
Mean = Σfi xi /Σfi
Mean salary = 305000/60
= 5083.33
Therefore, mean salary of 60 workers is Rs 5083.33.
Mddle block 1
Question : 6: Give one example of a situation in which
(i)The mean is an appropriate measure of central tendency.
(ii) The mean is not an appropriate measure of central tendency but the median is an appro-priate measure of central tendency.
Answer :
When any data has a few observations such that these are very far from the other obser-
vations in it, it is better to calculate the median than the mean of the data as median gives a
better estimate of average in this case.
(i) Consider the following example − the following data represents the heights of the members
of a family.
154.9 cm, 162.8 cm, 170.6 cm, 158.8 cm, 163.3 cm, 166.8 cm, 160.2 cm
In this case, it can be observed that the observations in the given data are close to each other.
Therefore, mean will be calculated as an appropriate measure of central tendency.
(ii)The following data represents the marks obtained by 12 students in a test.
48, 59, 46, 52, 54, 46, 97, 42, 49, 58, 60, 99
In this case, it can be observed that there are some observations which are very far from other
observations. Therefore, here, median will be calculated as an appropriate measure of central
tendency.
