Overview
Unit 9: Are you Confident?
Sample statistics, such as the sample mean or the sample proportion, can be used to estimate a population parameter (such as the population mean or the population proportion). For example, you can estimate the true mean weight of all full-term newborn babies in the entire world by collecting a sample and using that sample to generate a 95% confidence interval.
Because the sample is typically a relatively small portion of the entire population, errors will have to be considered. Using a sample to create a range or interval of values that estimates a population parameter is called a "confidence interval."
Post 1: Initial Response
- Select a dataset with between 30 and 100 values of continuous numeric data. If the data set has more than 100 values, randomly select between 30 and 100 of them. In your own words, why do you think it is impossible to know the actual value of any population parameter?
- A sample can be used to estimate a population parameter. How does the sample size affect the estimate?
- To estimate a population parameter (such as the population mean or population proportion) using a confidence interval requires that one first calculate the margin of error, E. The value of the margin of error, E, can be calculated using the appropriate formula. The formula depends on whether one is estimating a mean or estimating a proportion.
- A 95% Margin of Error, E, for a means is: , where s is the sample standard deviation and n is the sample size. We can say this because the sample size is at least 30, so we can estimate using the normal distribution and 95% of a normal distribution is between and .
- Select a data sample with between 30 and 100 values of continuous numeric data. You can find many . Use an Excel spreadsheet or the units 2 and 9 & 10 Excel templates (see link in resources to the left) to calculate the sample mean, the sample standard deviation, and the margin of error for your data set. If you create 30 values, the sample size is 30.
- A 95% Margin of Error, E, for a means is: , where s is the sample standard deviation and n is the sample size. We can say this because the sample size is at least 30, so we can estimate using the normal distribution and 95% of a normal distribution is between and .