tells us the likelihood of some effect being zero in our population. a zero effect means that all means are exactly equal for some factor such as gender or experimental group. however, some effect just being not zero isn't too interesting, is it? what we really want to know is: how ...
In order for your survey to be representative for an entire population, you need to calculate the number of respondents: the survey sample size. Here's how!
Here we have a simple random sampling, meaning that every possible combination of $n$ units from a population of size $N$ is equally likely to be the sample selected. We are in a sampling situation where the object is to estimate the proportion of units in a population ha...
The Formula When we don't have an estimate of the total population that we can use tocalculate standard deviation, we assume that it is equal to 0.5, because that will give us a conservative sample size to ensure that we are sampling a representative portion of the population; call this v...
To determine a sample size that will provide the most meaningful results, researchers first determine the preferred margin of error (ME) or the maximum amount they want the results to deviate from the statistical mean. It's usually expressed as a percentage, as in plus or minus 5 percent. ...
How to Estimate Statistical Characteristics Based on a Sample: Nonparametric Maximum Likelihood Approach Leads to Sample Mean, Sample Variance, etc.In many practical situations, we need to estimate different statistical characteristics based on a sample. In some cases, we know that the corresponding ...
This step asks you to estimate how much the responses you receive will vary from each other and from the mean number. A low standard deviation means that all the values will be clustered around the mean number, whereas a high standard deviation means they are spread out across a much wider...
margin of error, thelevel of confidence, and the standard deviation of the population we are investigating. Many times, it is impossible to know what the population standard deviation is. With the range rule, we can estimate this statistic, and then know how large we should make our sample....
Get a random sample of the population. If your sample is not random, estimates of the proportion (and other quantities) may be biased. For example, if you want to estimate the proportion of boys in an elementary school, you could assign a number to each student, then randomly pick a sam...
Estimate the proportion of the largest group. If you are unsure, use 0.5 as the expected proportion because the closer the two proportions, larger the sample size you will need. For example, if you expected 60 percent of people to vote for the incumbent, you would use 0.6. ...