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#1




95% Of the Population
A random sample of 100 12yearold boys were chosen and the heights of these 100 boys recorded. The sample mean height is 64 inches, and the sample standard deviation is 5 inches. Assuming heights of 12yearold boys are normally distributed. Which interval below includes approximately 95% of the heights of 12yearold boys?
a. 63 to 65 inches. b. 39 to 89 inches. c. 54 to 74 inches. d. 59 to 69 inches. e. Cannot be determined from the information given. f. Can be determined from the information given, but none of the above choices is correct. 
#2




because this is a normal distribution curve ...
mean=median=mode in such a curve 95% CI is the mean +/ 2 SD ie 64 +/ 2x5 ie 64+/ 10 so 5474 ie C 
#3




why not A.....using standard error of mean?

#4





#5




For interval we use the formula
interval = mean +/ Z(sd/n½) so interval = 64 +/ 2(5/10) {at 95 % ci z = 2) = 63 or 65 so A
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#6




Quote:
so u just use the +/ 2 SD formula for 95% CI right?? 
#7




No idea.. I guess you are right .. May be this formula doesnt apply for Normal distribution.. will have to check it.
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Don`t Let Others Tell You What You Cannot Do !!!! 
#8




at tyagee...i meant the formula used below by others to arrive at the option A...
I have always known wen u are given the sample size population u have to use the said formula... If not...use Mbbs2010 direct method ...cheers 
The above post was thanked by:  
mbbs2010 (07162012) 
Tags 
BiostatisticsEpidemiology, Step2Questions 
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