95 Confidence Interval Calculator Margin Error
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Margin Of Error Calculator Without Population Size
for a Sample… Statistics Essentials For Dummies Statistics For Dummies, 2nd Edition SPSS Statistics for Dummies, 3rd Edition Statistics margin of error excel II for Dummies Load more EducationMathStatisticsHow to Calculate the Margin of Error for a Sample Proportion How to Calculate the Margin of Error for a Sample Proportion Related Book Statistics For Dummies, how to find margin of error on ti 84 2nd Edition By Deborah J. Rumsey When you report the results of a statistical survey, you need to include the margin of error. The general formula for the margin of error for a sample proportion (if certain conditions are met) is where is the sample proportion, n is the sample size, and z* is the appropriate z*-value for your desired level of confidence
Margin Of Error Calculator With Standard Deviation
(from the following table). z*-Values for Selected (Percentage) Confidence Levels Percentage Confidence z*-Value 80 1.28 90 1.645 95 1.96 98 2.33 99 2.58 Note that these values are taken from the standard normal (Z-) distribution. The area between each z* value and the negative of that z* value is the confidence percentage (approximately). For example, the area between z*=1.28 and z=-1.28 is approximately 0.80. Hence this chart can be expanded to other confidence percentages as well. The chart shows only the confidence percentages most commonly used. Here are the steps for calculating the margin of error for a sample proportion: Find the sample size, n, and the sample proportion. The sample proportion is the number in the sample with the characteristic of interest, divided by n. Multiply the sample proportion by Divide the result by n. Take the square root of the calculated value. You now have the standard error, Multiply the result by the appropriate z*-value for the confidence level desired. Refer to the above table for the appropriate z*-value. If the confidence level is 95%, the z*-value is 1.96. Here's an example: Suppose that the Gallup Or
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Sampling Error Calculator
Friends Margin of Error In a confidence interval, the range of values above and below the sample statistic is called the margin of error. For example, suppose we wanted to know the http://www.dummies.com/education/math/statistics/how-to-calculate-the-margin-of-error-for-a-sample-proportion/ percentage of adults that exercise daily. We could devise a sample design to ensure that our sample estimate will not differ from the true population value by more than, say, 5 percent (the margin of error) 90 percent of the time (the confidence level). How to Compute the Margin of Error The margin of error can be defined by either of the following equations. http://stattrek.com/estimation/margin-of-error.aspx Margin of error = Critical value x Standard deviation of the statistic Margin of error = Critical value x Standard error of the statistic If you know the standard deviation of the statistic, use the first equation to compute the margin of error. Otherwise, use the second equation. Previously, we described how to compute the standard deviation and standard error. How to Find the Critical Value The critical value is a factor used to compute the margin of error. This section describes how to find the critical value, when the sampling distribution of the statistic is normal or nearly normal. The central limit theorem states that the sampling distribution of a statistic will be nearly normal, if the sample size is large enough. As a rough guide, many statisticians say that a sample size of 30 is large enough when the population distribution is bell-shaped. But if the original population is badly skewed, has multiple peaks, and/or has outliers, researchers like the sample size to be even larger. When the sampling distribution is nearly normal, the critical value can be expressed as a t score or as a z score
larger amount of error than if the respondents are split 50-50 or 45-55. Lower margin of error requires a larger sample size. What confidence level do http://www.raosoft.com/samplesize.html you need? Typical choices are 90%, 95%, or 99% % The confidence level is https://www.youtube.com/watch?v=dNfpsVLaaEE the amount of uncertainty you can tolerate. Suppose that you have 20 yes-no questions in your survey. With a confidence level of 95%, you would expect that for one of the questions (1 in 20), the percentage of people who answer yes would be more than the margin of error away from the true answer. The true answer margin of is the percentage you would get if you exhaustively interviewed everyone. Higher confidence level requires a larger sample size. What is the population size? If you don't know, use 20000 How many people are there to choose your random sample from? The sample size doesn't change much for populations larger than 20,000. What is the response distribution? Leave this as 50% % For each question, what do you expect the results will margin of error be? If the sample is skewed highly one way or the other,the population probably is, too. If you don't know, use 50%, which gives the largest sample size. See below under More information if this is confusing. Your recommended sample size is 377
This is the minimum recommended size of your survey. If you create a sample of this many people and get responses from everyone, you're more likely to get a correct answer than you would from a large sample where only a small percentage of the sample responds to your survey. Online surveys with Vovici have completion rates of 66%! Alternate scenarios With a sample size of With a confidence level of Your margin of error would be 9.78% 6.89% 5.62% Your sample size would need to be 267 377 643 Save effort, save time. Conduct your survey online with Vovici. More information If 50% of all the people in a population of 20000 people drink coffee in the morning, and if you were repeat the survey of 377 people ("Did you drink coffee this morning?") many times, then 95% of the time, your survey would find that between 45% and 55% of the people in your sample answered "Yes". The remaining 5% of the time, or for 1 in 20 sand Margin of Error statisticsfun SubscribeSubscribedUnsubscribe49,73349K Loading... Loading... Working... Add to Want to watch this again later? Sign in to add this video to a playlist. Sign in Share More Report Need to report the video? Sign in to report inappropriate content. Sign in Transcript Statistics 153,909 views 780 Like this video? Sign in to make your opinion count. Sign in 781 16 Don't like this video? Sign in to make your opinion count. Sign in 17 Loading... Loading... Transcript The interactive transcript could not be loaded. Loading... Loading... Rating is available when the video has been rented. This feature is not available right now. Please try again later. Uploaded on Jul 12, 2011Tutorial on how to calculate the confidence interval and margin of error (interval estimate). Include an example and some discussion on the bell curve and z scores.Like MyBookSucks on: http://www.facebook.com/PartyMoreStud...Related Videos:Z scores and Normal Tableshttp://www.youtube.com/watch?v=q5fwCl... How to Normalized Tables Used for Z scoreshttp://www.youtube.com/watch?v=dWu0KL...Playlist t tests for independent and dependent means.http://www.youtube.com/playlist?list=...Created by David Longstreet, Professor of the Universe, MyBookSuckshttp://www.linkedin.com/in/davidlongs... Category Education License Standard YouTube License Show more Show less Loading... Advertisement Autoplay When autoplay is enabled, a suggested video will automatically play next. Up next How to calculate Margin of Error Confidence Interval for a population proportion - Duration: 8:04. statisticsfun 42,511 views 8:04 How to calculate sample size and margin of error - Duration: 6:46. statisticsfun 64,220 views 6:46 How to calculate z scores - Duration: 9:34. statisticsfun 48,369 views 9:34 How to use Excel to Calculate Confidence Interval - Duration: 4:59. statisticsfun 304,977 views 4:59 Margin of Error Example - Duration: 11:04. drenniemath 36,716 views 11:04 Confidence Intervals Part I - Duration: 27:18. ProfessorSerna 163,283 views 27:18 How to calculate margin of error and standard d