Chapter 8 - KVANLI PAVUR KEELING Chapter8...

Info iconThis preview shows pages 1–16. Sign up to view the full content.

View Full Document Right Arrow Icon
Click to edit Master subtitle style   Chapter 8 Statistical  Inference and  Sampling KVANLI PAVUR KEELING
Background image of page 1

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

View Full DocumentRight Arrow Icon
3/10/11 Chapter Objectives At the completion of this chapter, you should be able to: ∙ Define and distinguish between sample statistics and population parameters ∙ Discuss the Central Limit Theorem and
Background image of page 2
3/10/11 What’s New in This Chapter? Usually population means (μ) are unknown and have to be estimated To estimate μ, get a sample and find the sample mean, X X estimates μ This is a parameter since it describes the population This is a statistic since it is derived from a sample
Background image of page 3

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

View Full DocumentRight Arrow Icon
3/10/11 Estimating the Population Mean This chapter discusses how good (reliable) this estimate is The first two sections in this chapter pretend that the population mean (μ) is known We do this to get some idea how the sample mean, X, “behaves”
Background image of page 4
3/10/11 How Does the Sample Mean Behave? Suppose we were to get sample after sample, finding the sample mean each time If we put these sample means into Excel and told it to make a histogram, what would it look like In particular, does the histogram have a bell-shaped (normal) appearance?
Background image of page 5

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

View Full DocumentRight Arrow Icon
3/10/11 Example 8.2 Remember : For the first two sections, we’re pretending we know the population mean, μ In this example, we’re interested in X = lifetime of a high-intensity light bulb This example contains 20 samples of n = 10 bulbs each
Background image of page 6
3/10/11 The Population Shape for X = Lifetime of Bulb μ = X 450 500 550 350 300 250 Bulb lifetimes (in hours) are in here σ is 50 hours
Background image of page 7

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

View Full DocumentRight Arrow Icon
3/10/11 20 Samples: X = Lifetime of Bulb Columns Q, R, S, T contain the last four samples Column V contains the 20 sample means followed by a summary of these means Column W contains the 20 sample standard deviations Notice 1) The sample means are hanging around 400 2) The sample standard deviations are hanging around 50
Background image of page 8
3/10/11 The Main Thing The sample means don’t jump around as much (they have less variation) as the individual values Look at the variation in any of the samples in columns Q, R, S, and T Observe how much more variation there is in these four samples as compared to the This is much less than 50
Background image of page 9

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

View Full DocumentRight Arrow Icon
3/10/11 X = Male Height X = Ht. . 25 6’ 6.25’ 6.5’ 5.5’ . 25 5.25’ 5’ Nearly all heights are in here This is picture #1: the shape of the population
Background image of page 10
3/10/11 Looking at the Sample Means: Picture #2 5.75’ X 5.775’ 5.8’ 5.825 5.725’ 5.7’ 5.675 Nearly all sample means are in here This is the curve describing the average of n = 100 heights (measureme nts) ' 025 . 10 ' 25 . 100 ' 25 . = = This is a skinny normal curve
Background image of page 11

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

View Full DocumentRight Arrow Icon
3/10/11 A Whole Lot of Heights The spreadsheet shown on the next two slides contains 50 samples of male heights Each sample contains 100 heights These are not actual heights but were computer generated Each sample was selected from a normal population with a mean of
Background image of page 12
3/10/11 The First 5 Samples of Heights The first 12 rows The last 5 rows
Background image of page 13

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

View Full DocumentRight Arrow Icon
3/10/11 The Last 5 Samples of Heights The first 12 rows The last 5 rows
Background image of page 14
3/10/11 First Question What proportion of male heights is > 5.8’?
Background image of page 15

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

View Full DocumentRight Arrow Icon
Image of page 16
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 03/09/2011 for the course DSCI 2710 taught by Professor Hossain during the Fall '08 term at North Texas.

Page1 / 83

Chapter 8 - KVANLI PAVUR KEELING Chapter8...

This preview shows document pages 1 - 16. Sign up to view the full document.

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