EASY
Earn 100

The quartile deviation of a normal distribution with mean 10 and standard deviation 4 is __________

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Important Questions on Interpreting Categorical and Quantitative Data

HARD
The standard deviations of xii=1,2,.10 and yii=1,10 are respectively a and bx¯, y¯ are the means of these two sets of observations respectively. If zi=xi-x¯yi-y¯ and i=110zi=c, then the standard deviation of the observations xi-yi, i=1,2,10 is
MEDIUM
For a certain type of mobiles, the length of time between charges of the battery is normally distributed with a mean of 50 hours and a standard deviation of 15 hours. A person owns one of these mobiles and wants to know the probability that the length of time will be between 50 and 70 hours is (Given ϕ1.33=0.9082,ϕ0=0.5)
MEDIUM
For a group of 100 students, the mean x¯1 and the standard deviation σ1 of their marks were found to be 40 and 15 respectively. Later it was observed that the scores 40 and 50 were misread as 30 and 60 respectively. If the mean and the standard deviation with the corrected observations of the scores are x¯2 and σ2 respectively, then
HARD
Let n3 . A list of numbers 0<x1<x2<<xn has mean μ and standard deviation σ . A new list of numbers is made as follows: y1=0, y2=x2,.,yn-1=xn-1,yn=x1+xn . The mean and the standard deviation of the new list are μ^ & σ^ . Which of the following is necessarily true?