1234
Points: 2Question 2
Ten employees of a nursing home, having been given a course in cardiopulmonary resuscitation (CPR), scored 17, 20, 12, 14, 18, 23, 17, 19, 18, and 15 on a test administered after the completion of the course. Find the standard deviation and variance.
Standard deviation = 2.97; Variance = 8.81
Standard deviation = 8.81; Variance = 8.81
Standard deviation = 8.81; Variance = 2.97
Standard deviation = 3.13; Variance = 9.59

- anonymous

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- anonymous

@ZoMbAsH

- anonymous

@welshfella
@TheSmartOne

- welshfella

hmm see if i remember this
First find the mean of all the values by adding up all the values then dividing by 10

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## More answers

- anonymous

k

- anonymous

17.3

- welshfella

the subtract the mean from each of the values
so for 17 this will give 17-17.3 = -0.7
do this for all 10 values

- anonymous

I'll be honest I have no idea :(

- anonymous

why u choose 17?

- welshfella

just as an example

- anonymous

oh i see

- welshfella

then you square each of the results and add them up. Finally divide the total by n

- welshfella

|dw:1435251903888:dw|

- anonymous

i dont no what the or the upside down h is

- welshfella

where mu is the mean and Sigma means the total sum

- welshfella

the n is total number of readinsg = 10

- welshfella

thats the variance
the standard deviation is the square root of the variabce

- welshfella

* variance

- triciaal

be careful with your computation

- welshfella

I'm relying in memory but i think this is right

- welshfella

maybe triciaal will confirm?

- anonymous

so far i got -0.3, 2.7, -5.3, -3.3, 0.7, 5.7,-0.3, 1.7, 0.7, -2.3

- welshfella

Ok so you square each one of these

- welshfella

0.09, 7.29 etc

- anonymous

ok

- welshfella

now add them up then divide by 10

- anonymous

0.09, 7.29, 28.09, 10.89, 0.49, 32.49, 0.09, 2.89, 0.49, 5, 29

- welshfella

look s good

- triciaal

@welshfella your process is fine, formula is correct, great job
I was referring to the simple stuff 17 - 17.3 not = -0.7

- anonymous

i got 9,807? wait did i do that wrong

- triciaal

@jordanawest22 did you actually find the mean?

- anonymous

i subtracted everythin from 17.3...ex)17-17.3....then i added them and divided by 10 and got , 8.807

- triciaal

no after you subtract you square each then add before dividing by N

- anonymous

what?, but the answer is up there??????

- welshfella

i'm getting a bit confused myself!!!!!
its value - mean right?

- anonymous

thats what i did

- triciaal

|dw:1435256442515:dw|

- welshfella

so the first 1 is 17-17.3 = -0.3

- triciaal

for the X each entry in the data here I have 1,2,3,4,5,

- anonymous

i found the mean of the numberss in the question then i subtrated the mean by all of the units in the problem, i got mostly decimals...then i squared them all then added them then divided by 10

- welshfella

yes thats correct
- - i think its best to put it in a table as triciall has
then you are less likely to make errors

- anonymous

ok, i got 8.81 so that would be the variance right?

- welshfella

i got 8.81 for the variance

- welshfella

yes

- anonymous

and to find the variance i do what now?

- welshfella

8.81 is the variance
std dev = square root of the variance

- triciaal

|dw:1435256789840:dw|

- welshfella

sqrt 8.81 = ?

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