math check and help
posted by Tom 81 .
A random sample of the amount paid (in dollars) for taxi fare from downtown to the airport was obtained. (Give your answers correct to two decimal places.)
16 17 22 13 21 23 22 18 13 22 19 20 19 22 16
(a) Use the data to find a point estimate for the mean.
$ 18.87 .
(b) Use the data to find a point estimate for the variance.
$ I have a problem getting variance
(c) Use the data to find a point estimate for the standard deviation.
$ I have a problem getting sd.

I would do c) first
probably the most common method to find the SD
is to take differences between each of the given data values and the mean.
This will give you 15 differences, some positive , some negative
make a new list of the square of each of these differences.
Add up these squares and divide that sum by 14
(one less than the number of data values, you might want to check with your text or notes on this one, some divide by n itself, the number of data values)
Take the square root of that division answer and that is your SD
b) variance = (SD)^2
here is a page illustrating SD vs variance
http://stats.stackexchange.com/questions/35123/whatsthedifferencebetweenvarianceandstandarddeviation
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