Sat, Jul 26, 2014, 2:09 AM EDT - U.S. Markets closed

## Recent

% | \$
 Click the  to save as a favorite.

# KVH Industries Inc. Message Board

you are viewing a single comment's thread.

view the rest of the posts
• MVLA MVLA Dec 15, 2003 7:23 PM Flag

## Standard deviation

I have a little experience in statistics. If you have a population of 500, you would have to randomly select 83 to have precision rate of +/- 10% at a 95% confidence level. If you wanted to be +/- 5% at a 95% confidence level, you would need to sample 222.

I know it does't make intuitive sense, but a sample of 1,111 of our US population gives you a precision rate of +/- 3% at a 95% confidence level.

SortNewest  |  Oldest  |  Most Replied Expand all replies
• Bob,

A 95% confidence interval for a population mean(average) involves finding the max. error of estimate E which is then added and subtracted to the sample mean to obtain the interval.
E is found by the following calculation:

E = 1.96 * s/square root of n

where n is the sample size and s is the standard deviation of the sample.

Excel has the capability of finding the mean and s for a set of data which is highlighted using the statistical functions therein.

Hypothetical example: mean is 3. E= .9
Interval would be 2.1 to 3.9 where one can be 95% sure that the true population mean will fall.

Probably a good idea to throw out any outliers such as an outlet which may have sold 12 where nobody else sold more than 7. A sample size of 50 chosen RANDOMLY would probably lead to a reasonable value.

Good luck

## Top Stories

13.63-0.20(-1.45%)Jul 25 3:59 PMEDT

## Trending Tickers

i
Trending Tickers features significant U.S. stocks showing the most dramatic increase in user interest in Yahoo Finance in the previous hour over historic norms. The list is limited to those equities which trade at least 100,000 shares on an average day and have a market cap of more than \$300 million.
##### El Pollo Loco Holdings, Inc.
NasdaqFri, Jul 25, 2014 4:00 PM EDT
##### AcelRx Pharmaceuticals, Inc.
NasdaqGMFri, Jul 25, 2014 3:59 PM EDT
##### Burger King Worldwide, Inc.
NYSEFri, Jul 25, 2014 4:01 PM EDT