For the following questions answer them individually
Mean marks secured by the students in a class is 53. The mean marks of girls, is 55 and mean marks of the boys is 50. The percentage of girls in the class is
$$x_1, x_2, x_3$$ are ungrouped data with $$x_1 > x_2 > x_3$$. If the arithmetic mean and median of this data are respectively 30 and 20 and $$x_1 - x_3 = 50$$, then $$x_3 =$$
The median of four observations is 4 and their mode is 6. If the sum of the squares of those observations is 48, then their standard deviation is
A population with two groups has 250 items with mean 15.6 and variance 13.44. The first group of 100 items has mean 15 and variance 9. Then the standard deviation of the second group is
The height $$x$$ (in cms) and the weight y (in kgs) of 5 students are given below:
The coefficient of con-elation $$\rho_{xy}$$ between their heights and weights is nearly
In a lottery of 118 tickets numbered 1 to 118. three tickets are drawn at random simultaneously. The probability that all the tickets drawn have prime numbers is
A student appears for tests I, II and III. He will be successful if he passes through either Test I and Test II or Test I and Test III. The probability of a student passing the tests I, II, III are p. q, $$\frac{1}{2}$$ respectively. If the probability that a student is successful is $$\frac{1}{2}$$, then which one of the following is true?
A bag contains 20 red and green tennis balls. of which 8 are marked 'used' and 12 are red. If the probability of picking a green marked 'used' ball is 1/5, the probability of picking a reel unmarked ball from the bag is
A $$2 \times 2$$ matrix having elements 0 and 1 is selected at random. The probability that it is a non-singular matrix is