NCERT class 11 maths chapter 15 Statistics
Question 1:The mean and variance of eight observations are 9 and 925, respectively. If six of the observations are 6, 7, 10, 12, 12 and 13, find the remaining two observations.
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Question 2:The mean and variance of 7 observations are 8 and 16, respectively. If five of the observations are 2, 4, 10, 12, 14. Find the remaining two observations.
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Question 3:The mean and standard deviation of six observations are 8 and 4, respectively. If each observation is multiplied by 3, find the new mean and new standard deviation of the resulting observations.
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Question 4:Given that x is the mean and s2 is the variance of n observations x1, x2, ...,xn. Prove that the mean and variance of the observations ax1, ax2, ax3, ...., axn are a x and a2 s2, respectively, (a ¹ 0).
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Question 5:The mean and standard deviation of 20 observations are found to be 10 and 2, respectively. On rechecking, it was found that an observation 8 was incorrect. Calculate the correct mean and standard deviation in each of the following cases: (i) If wrong item is omitted. (ii) If it is replaced by 12.
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Question 6:The mean and standard deviation of marks obtained by 50 students of a class in three subjects, Mathematics, Physics and Chemistry are given below: Subject Mathematics Physics Chemistry Mean 42 32 40.9 Standard 12 15 20 deviation Which of the three subjects shows the highest variability in marks and which shows the lowest?
Question 7:The mean and standard deviation of a group of 100 observations were found to be 20 and 3, respectively. Later on it was found that three observations were incorrect, which were recorded as 21, 21 and 18 Find the mean and standard deviation if the incorrect observations are omitted.
