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The mean and standard deviation of 100 o...

The mean and standard deviation of 100 observations were calculated as 40 and 5.1 respectively by a student who took by mistake 50 instead of 40 for one observation. What are the correct mean sand standard deviation?

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`barx=1/n sum_(i=1)^nx_i`
`=>sumx_i=nbarx`
`=100xx40`
`=4000`
...
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