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mathwonka

Guest

S1 standard deviation help?

hi,

ok, the question this time is this;

"1) An adult evening class has 14 students. The ages of these students have a mean of 31.2 years and a standard deviation of 7.4 years.

A new student who is exactly 42 years old joins the class. Calculate the mean and standard deviation of the 15 students now in the group. (7 marks)"

calculating the new mean:

so I think 31.92 is the new mean, i think?

but it also asks for the new standard deviation, and here i'm stuck.

what do i do here? i think i "kind of" know what to do but i'm not sure how to do it.

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: S1 standard deviation help?

Hi;

You are correct on the new mean.

Would you say that your mean is a sample mean or a population mean?

I need to know which formula you use for the standard deviation.

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