A group of 6 scores has a standard deviation of 0. Which of these conclusions is

Question

A group of 6 scores has a standard deviation of 0. Which of these conclusions is true? b. c. d. All the subjects had the same score. A computational error was made. None of the above is correct. 21. If 5 points are added to each score in a distribution, which of the following will happen? a. the mean will be unchanged b. the mode will be unchanged c. the standard deviation will be unchanged d. the mean, median, and mode will be unchanged 22. In a normal distribution, what is the percentile rank of a z-score of zero? a. c. 50 d. 34 23. A person's raw score is 50, with a value of Z. -1. The person's percentil rank is (approximately) a. b. c. 34% 16% 84%

Explanation / Answer

(20) b,all subject had same score

standard deviation=sd=sqrt(sum(xi-x-)2/n), sd will be zero, only if all xi =x- i.e. every observation is same

(21)c, standard deviation

mean,median and mode are dependent on change of origin but standard deviation is inpendent of change of origin

here we are adding 5 to each observation so it is change of origin

(22)c.50

P(Z<0)=0.5 , 50th percentile

(23)b 16%

P(Z<-1)=0.1587 ( using ms-excel=normsdist(-1))

so it is 16 percentile approximately

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