- #1

chwala

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- Homework Statement
- see attached

- Relevant Equations
- statistics

Find the textbook problem here;

Find the textbook solution here:

Now, to my question, did the textbook guys make an error on the value of ##σ?##, see my working;

Mean (##13## boys)=##\dfrac{153.4+(148.8×12)}{13}=149.15##

We know that,

##29.16##=##\dfrac{\sum x^2}{12}##-##(148.8)^2##

##\sum x^2=266,047.2##

Now, it follows that, ##266,047.2+153.4^2=289,578.76##

Variance=##\dfrac{289,578.76}{13}##-##(149.15)^2##

Variance=##29.56673077##

Standard deviation=##\sqrt {29.56673077}=5.4375##

Find the textbook solution here:

Mean (##13## boys)=##\dfrac{153.4+(148.8×12)}{13}=149.15##

We know that,

##29.16##=##\dfrac{\sum x^2}{12}##-##(148.8)^2##

##\sum x^2=266,047.2##

Now, it follows that, ##266,047.2+153.4^2=289,578.76##

Variance=##\dfrac{289,578.76}{13}##-##(149.15)^2##

Variance=##29.56673077##

Standard deviation=##\sqrt {29.56673077}=5.4375##

Last edited: