STATISTICS (CDS)

Total Questions: 63

31. The mean marks obtained by 300 students in a subject are 60. The mean of top 100 students was found to be 80 and the mean of last 100 students was found to be 50. The mean marks of the remaining 100 students are

Correct Answer: (d) 50
Solution:

32. For x > 0 if a variable takes discrete values x + 4, x - 35, x - 25, x - 3, x - 2, x + 0.5, x - 0.5 x + 5 , then what is the median?

Correct Answer: (a) x - 125
Solution:

33. The median of set of 9 distinct observations is 20 5. . If each of the largest 4 observations of the set is increased by 2, then the median of the new set

Correct Answer: (d) remains the same as that of original set
Solution:

34. The mean of 20 observations is 17. On checking it was found that the two observations were wrongly copied as 3 and 6. If wrong observations are replaced by correct values 8 and 9, then what is the correct mean?

Correct Answer: (a) 17.4
Solution:

35. Consider the following statements.

I. The classes of type 15-19, 20-24, 25-29 etc, are exclusive classes.
II. The classes of type 15-20, 20-25, 25-30 etc, are inclusive classes.

Which of the above statements is/are correct?

Correct Answer: (d) Neither I nor II
Solution:In exclusive classes, upper limit of a class is not included in the class. So, 15-20, 20-25, 25-30 are exclusive classes. In inclusive classes, upper limit of a class is included in the class.
So, 15-19, 20-24, 25-29 are inclusive classes. Hence, neither statement I nor statement II are correct.

36. Suppose the class interval 10-15 has frequency 30, then what is the frequency density of this class interval?

Correct Answer: (d) 6
Solution:

37. If the mean age of combined group of boys and girls is 18 yr and the mean of age of boys is 20 and that of girls is 16, then what is the percentage of boys in the group?

Correct Answer: (b) 50
Solution:

38. The election result in which six parties contested was depicted by a pie chart. Party A had an angle 135° on this pie chart. If it secured 21960 votes, then how many valid votes in total were cast?

Correct Answer: (b) 58560
Solution:

39. The mean and median of 5 observations are 9 and 8, respectively. If 1 is subtracted from each observation, then the new mean and the new median will respectively be

Correct Answer: (a) 8 and 7
Solution:

40. The age distribution of 40 children are as follows

Consider the following statements in respect of the above frequency distribution
1. The median of the age distribution is 7 year.
2. 70% of the children are in the age group 6-9 year.
3. The modal age of the children is 8 year.

Which of the above statements are correct?

Correct Answer: (b) 2 and 3
Solution: