Statistics 101 - Sample and Sampling Distribution

• Point Estimation
• We can't get population parameter directly (mean of income of your country) so that need to take samples to estimate it (inference)
• Sample never perfect

• Sampling and Sampling Distribution
• Take many random samples from unknown population
• The mean of the sampling distribution (based on taken sample means) is equal to the mean of population 
• (랜던 샘플을 많이 가져와서 그 분포의 mean을 보면 실제 population의 mean과 같다)

• Standard deviation of sample mean
• Note standard deviation becomes smaller when sample size(n) increases
• Same sample size has the same standard error of the mean
• Standard Error
• another name for the standard deviation. It is just the standard deviation of the sampling distribution