This document discusses how to calculate a confidence interval for a mean. It outlines that the sampling distribution must be approximately normally distributed and use simple random sampling. It describes the steps as calculating the sample statistic, choosing a confidence level, determining the margin of error using the standard deviation or standard error, and specifying the confidence interval as the sample statistic plus or minus the margin of error. It also notes that when the population is at least 10 times the sample size, the standard error can be approximated from tables, and when the population standard deviation is unknown, a t-score must be used instead.
2. Confidence Interval for a mean (x)
Estimation Requirements:
1. Simple Random Sampling
2. Sampling distributed is approximately normally distributed
How to find a CI for a Mean
(method same as described before)
1. sample statistic (use sample proportion to estimate population
proportion)
2. CL (90%, 95%, 99%)
3. ME= CV x SD or ME= CV x SE
4. Specify CI: sample statistic + ME
written as: (Sample Stat – ME, Sample Stat + ME)
3. Variability of Sample Mean
• Must compute SE of sampling distribution
• When the population is at least 10 times bigger than the sample
size, we can approximate the SE:
** this is found on the table under single-sample mean
When you do not have the population SD (which is usually the case)
must use a t-score.
