handout_6_1_fall11(1) - 6.1 Estimating with Confidence give...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: 6.1 Estimating with Confidence give Test Y to an SRS of 400 students, x = 500 What can you say about the mean score in population? x is an unbiased estimator of ( x = ) but how reliable is this estimate? (how variable is the statistic?) recall x is approximately N (, n ) when n is large suppose population standard deviation = 100, then x = n = 400 100 = 5 (unrealistic to assume we would know - relax this assumption in Chapter 7) x has normal distribution centered at unknown population mean with x = 5 Confidence intervals the 68-95-99.7 rule says that, for any N distribution, 95% of observations within 2 sd of mean 95% chance x will be within 2 standard deviations of x 95% chance x will be within 10 points of population mean to say that x lies within 10 points of is the same as saying that is within 10 points of x so 95% of all samples will capture the true in the interval from x- 10 to x + 10 our sample gave x = 500 95% confidence interval= x 10 500 10 [490, 510] we say that we are 95% confident that the unknown mean score lies between [490, 510] Once we look at a sample and construct a confidence interval, there are two possibilities: 1) The interval between 490 and 510 contains the true population mean . Our sample is one of the 95% of samples where lies within 10 points of x . 2) The true population mean is not contained between 490 and 510 (rare result)....
View Full Document

Page1 / 7

handout_6_1_fall11(1) - 6.1 Estimating with Confidence give...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online