Chapter14

The Basic Practice of Statistics (Paper) & Student CD

Info iconThis preview shows pages 1–7. Sign up to view the full content.

View Full Document Right Arrow Icon
Confidence intervals: The basics BPS chapter 14 © 2006 W.H. Freeman and Company
Background image of page 1

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

View Full DocumentRight Arrow Icon
Objectives (BPS chapter 14) Confidence intervals: the basics Estimating with confidence Confidence intervals for the mean μ How confidence intervals behave Choosing the sample size
Background image of page 2
Estimating with confidence Although the sample mean, , is a unique number for any particular sample, if you pick a different sample, you will probably get a different sample mean. In fact, you could get many different values for the sample mean, and virtually none of them would actually equal the true population mean, μ . x
Background image of page 3

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

View Full DocumentRight Arrow Icon
But the sample distribution is narrower than the population distribution, by a factor of n . Thus, the estimates gained from our samples are always relatively close to the population parameter µ . n Sample means, n subjects μ n ! " Population, x individual subjects x x If the population is normally distributed N ( µ , σ ), so will the sampling distribution N ( µ , σ / n ).
Background image of page 4
Red dot: mean value of individual sample 95% of all sample means will be within roughly 2 standard deviations (2* σ / n ) of the population parameter μ . Because distances are symmetrical, this implies that the population parameter must be within roughly 2 standard deviations from the sample average , in 95% of all samples. " n This reasoning is the essence of statistical inference. x
Background image of page 5

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

View Full DocumentRight Arrow Icon
The weight of single eggs of the brown variety is normally distributed N (65g,5g). Think of a carton of 12 brown eggs as an SRS of size 12. You buy a carton of 12 white eggs instead. The box weighs 770g. The average egg weight from that SRS is thus = 64.2g. Knowing that the standard deviation of egg weight is 5g, what can you infer about the mean µ of the white egg population? There is a 95% chance that the population mean
Background image of page 6
Image of page 7
This is the end of the preview. Sign up to access the rest of the document.

This document was uploaded on 09/24/2008.

Page1 / 21

Chapter14 - Confidence intervals: The basics BPS chapter 14...

This preview shows document pages 1 - 7. Sign up to view the full document.

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