Research Methodology in Social Sciences

Fourth Meeting

• Estimation
• Lab

• Very often, we have to infer about population based on relatively small number of observations (sample)
• For instance, usually in the media polls are covered as parameters but they are estimates

• A good estimate has a sampling distribution which is centered around the parameter and has small standard error

• We are never sure how precise are our estimates, therefore it is safer to assume a particular margin that contains true population parameter by a high probability, say - close to 1
• This margin is called confidence interval. Confidence interval has a form: Point Estimate +/- margin of error (multiple of a standard error)
• Confidence intervals are chosen conventionally, usually, 95% or 99%

• \( \sigma_{\hat{\pi}} = {\sigma}/{n} = \sqrt{{\pi(1-\pi)}/{n}} \)

• \( \sigma_{\hat{x}} = {s}/{\sqrt{n}} \)