# Statistics Lectures - 16: Sample Proportions & Confidence Intervals About The Mean

A series of free Statistics Lectures with lessons, examples & solutions in videos.

This is the sixteenth page of the series of free video lessons, “Statistics Lectures”. These lectures discuss sample proportions, confidence intervals about the mean with population standard deviation known and calculating required sample size to estimate population mean.

### Statistics - Lecture 45: Sample Proportions

Example:
In a sample of 500 individuals, 75 are left handed. Describe the distribution of the sample proportion.

### Statistics - Lecture 46: Confidence Intervals About The Mean With Population Standard Deviation Known

The value of any statistic that estimates the value of a parameter is called a point estimate.
We rarely know if our point estimate is correct because it is merely an estimation of the actual value.

Example:
On the verbal section of the SAT, the standard deviation is known to be 100. A sample of 25 test-takers has a mean of 520. Construct a 95% confidence interval about the mean.

### Statistics - Lecture 47: Calculating Required Sample Size to Estimate Population Mean

We can calculate what sample size we will need in order to have a certain margin of error.

Example:
On the verbal section of the SAT, the standard deviation is known to be 100. What sample size would we need to construct a 95% confidence interval with a margin of error of 20? 