# Sample Size

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- This topic has 4 replies, 3 voices, and was last updated 15 years, 5 months ago by Tierradentro.

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- September 13, 2004 at 11:08 pm #36861

John in TexasParticipant@John-in-Texas**Include @John-in-Texas in your post and this person will**

be notified via email.I have 5000 item numbers in inventory. I need to calculate a sample size of items to count (inventory) to assure the results (dollars variance) will be a representation of the population with 95% confidence. I can risk a .5% error rate. Any suggestions?

Thanks, John0September 14, 2004 at 1:22 pm #107350No one has replied, is more information required?

0September 14, 2004 at 1:58 pm #107356Hi John,

Yes, to calculate the sample size you need your average error rate (%). Given that, the formula you need is:

n=p(1-p)(Z/E)squared

where:

p=average error rate (?)

Z = number of standard deviations associated with your confidence (in this case 1.96)

E = allowed error (0.5%)

Best Regards,

Bob J0September 14, 2004 at 2:01 pm #107357John,

You might like to take a look at a sample size calculator. One can be found at:

http://www.surveysystem.com/sscalc.htm

Of course, this approach assumes that all your items have the same value. Since you want to calculate a Dollar variance, you might want to do it by ‘value categories’. In other words, if a category has a high value, you might want to consider adjusting your confidence intervals accordingly.

Andy0September 14, 2004 at 8:18 pm #107390Thanks Bob!!

The average error rate was .250 - AuthorPosts

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