Marks obtains by all the students of class 12 are presented in a freqency distribution with classes of equal width. Let the median of this grouped data be 14 with median class interval 12-18 and median class frequency 12. If the number of students whose marks are less than 12 is 18 , then the total number of students is :
If the variance of the frequency distribution
$$x$$ | $$c$$ | $$2c$$ | $$3c$$ | $$4c$$ | $$5c$$ | $$6c$$ |
---|---|---|---|---|---|---|
$$f$$ | 2 | 1 | 1 | 1 | 1 | 1 |
is 160, then the value of $$c\in N$$ is
The frequency distribution of the age of students in a class of 40 students is given below.
Age | 15 | 16 | 17 | 18 | 19 | 20 |
---|---|---|---|---|---|---|
No of Students | 5 | 8 | 5 | 12 | $$x$$ | $$y$$ |
If the mean deviation about the median is 1.25, then $$4x+5y$$ is equal to :
The mean and standard deviation of 20 observations are found to be 10 and 2 , respectively. On rechecking, it was found that an observation by mistake was taken 8 instead of 12. The correct standard deviation is