Sample Planning Wizard As you may have noticed, the steps required to estimate a population proportion are not trivial. Keep this in mind when you hear reports in the media; the media often get this wrong. Forty percent of the sample wanted more local news. Exercise 4 shows the effect of of increasing the sample size on the SE of the sample proportion.

Proportion Author(s) David M. However, students are expected to be aware of the limitations of these formulas; namely, the approximate formulas should only be used when the population size is at least 20 times larger Therefore, multiplying the sample size by a certain factor divides the SE of by the squareroot of that factor Next: Exercises Up: Sampling Distribution of the Previous: The Sampling Suppose we take a sample of 40 graduating students, and suppose that 6 out of the 40 are planning to go to graduate school.

When the population size at least 20 times larger than the sample size, the standard error can be approximated by: SEp = sqrt[ p * ( 1 - p ) / Not the answer you're looking for? In practice, if the probability is quite close to one or to zero while you have few samples, the value given by the expression might have large error. This condition is satisfied; the problem statement says that we used simple random sampling.

For convenience, we repeat the key steps below. Identify a sample statistic. All Rights Reserved. Compute margin of error (ME): ME = critical value * standard error = 2.58 * 0.012 = 0.03 Specify the confidence interval.

b. Often, researchers choose 90%, 95%, or 99% confidence levels; but any percentage can be used. Can a Legendary monster ignore a diviner's Portent and choose to pass the save anyway? My CEO wants permanent access to every employee's emails.

SEp = sqrt[ p * ( 1 - p ) / n ] * sqrt[ ( N - n ) / ( N - 1 ) ] where p is the Can Communism become a stable economic strategy? Why does the material for space elevators have to be really strong? Share a link to this question via email, Google+, Twitter, or Facebook.

Therefore, the 99% confidence interval is 0.37 to 0.43. How to solve the old 'gun on a spaceship' problem? Stat Trek's Sample Planning Wizard does this work for you - quickly, easily, and error-free. How?

Browse other questions tagged standard-error proportion weighted-data or ask your own question. In practice, however, the word ``estimated'' is dropped and the estimated SE is simply called the SE . Specify the confidence interval. Suppose we classify a "more local news" response as a success, and any other response as a failure.

share|improve this answer answered Jun 29 '15 at 20:12 whuber♦ 145k17283542 Thanks! Wow, thanks for the clarification @Aniko...that wouldn't have been good to report. Make sure your sample sizes are large enough. –EngrStudent Jun 29 '15 at 17:59 add a comment| 1 Answer 1 active oldest votes up vote 5 down vote accepted Yes, this Generated Thu, 13 Oct 2016 17:56:20 GMT by s_ac4 (squid/3.5.20)

If the population size is much larger than the sample size, we can use an "approximate" formula for the standard deviation or the standard error. This means we need to know how to compute the standard deviation and/or the standard error of the sampling distribution. We then make a slight adjustment to correct for the fact that the distribution is discrete rather than continuous.

Normal Distribution Calculator sp is calculated as shown below: To correct Join them; it only takes a minute: Sign up Here's how it works: Anybody can ask a question Anybody can answer The best answers are voted up and rise to theFind the margin of error. This condition is satisfied, so we will use one of the simpler "approximate" formulas. The sample is sufficiently large. Let's suppose there are m 1s (and n-m 0s) among the n subjects.

I suppose I could've done the same to calculate SEM from the 95% confidence interval provided by prop.test too, but this is better. Lane Prerequisites Introduction to the Normal Distribution, Normal Approximation to the Binomial, Sampling Distribution of the Mean, Sampling Distribution of a Proportion, Confidence Intervals, Confidence Interval on the Mean Learning Objectives That is, the 99% confidence interval is the range defined by 0.4 + 0.03. In this analysis, the confidence level is defined for us in the problem.

Using the t Distribution Calculator, we find that the critical value is 2.58. I can calculate SD from SEM. Is it "eÄ‰ ne" or "ne eÄ‰"? Standard deviation refers to the variability of the original 0-1 variable. –Aniko May 20 '11 at 2:55 Oh!

The system returned: (22) Invalid argument The remote host or network may be down. Find the margin of error. When the population size is much larger (at least 20 times larger) than the sample size, the standard deviation can be approximated by: σp = sqrt[ P * ( 1 - This last term is called the standard error of estimation of the sample proportion, or simply standard error (SE) of the proportion .

Select a confidence level. The resulting quantity is called the estimated standard error of the sample proportion .