Can I get some help please? thanks!

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1 Answer
sjc · Geoff K.
Sep 20, 2017

#barx=16.1" (nearest tenth)"#

#sigma=3.6" (nearest tenth")#

Explanation:

The mean is the sum of the numbers divided by how many there are:

#barx=1/nsumx_i#

#barx=(20+16+18+14+9+20+16)/7#

#barx=113/7=16.1428....=16.1" (nearest tenth)"#

For the standard deviation, there are a several formulae one can use. Whichever one you use, there will be a lot of arithmetic to do!

We will use:

#sigma=sqrt(1/nsum(x_i-barx)^2#

We have to subtract the mean from each #x_i# value, square these differences, and then add:

#(20-113/7)^2=729/49#

#(16-113/7)^2=1/49#

#(18-113/7)^2=169/49#

#(14-113/7)^2=225/49#

#(9-113/7)^2=2500/49#

#(20-113/7)^2=729/49#

#(16-113/7)^2=1/49#

The sum is #(729+1+169+225+2500+729+1)/49=4354/49#

So

#sigma=sqrt(1/7xx(4354)/49)#

#sigma =sqrt622/7=3.56284.......#

#sigma=3.6" (nearest tenth")#

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