The following data comes from a sample of 20,000 adults randomly selected from a large group of people interviewed for a CDC survey in 2000. Below are the weights of all of the people in the sample, shown in a histogram.
The average weight was 170 lbs. with a standard deviation of about 40 lbs.
In a random sample, the sample mean x̄ is random, so it has a probability distribution with a shape, center, and spread. To get an idea of what the sampling distribution is for different size samples, just click the button below:
When the sampling distribution for x̄ looks like: