Sampling distributions stat ppt @ bec doms

Chapter Goals ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],_ _ _ _

Sampling Error ,[object Object],[object Object],[object Object],[object Object],[object Object]

Calculating Sampling Error ,[object Object],[object Object],[object Object],[object Object]

Review ,[object Object],where: μ = Population mean x = sample mean x i = Values in the population or sample N = Population size n = sample size

Example If the population mean is μ = 98.6 degrees and a sample of n = 5 temperatures yields a sample mean of = 99.2 degrees, then the sampling error is

Sampling Errors ,[object Object],[object Object],[object Object],[object Object]

Sampling Distribution ,[object Object]

Developing a Sampling Distribution ,[object Object],[object Object],[object Object],[object Object],A B C D

Developing a Sampling Distribution .3 .2 .1 0 18 20 22 24 A B C D Uniform Distribution P(x) x (continued) Summary Measures for the Population Distribution:

Now consider all possible samples of size n=2 16 possible samples (sampling with replacement) (continued) Developing a Sampling Distribution 16 Sample Means

Sampling Distribution of All Sample Means 18 19 20 21 22 23 24 0 .1 .2 .3 P(x) x Sample Means Distribution 16 Sample Means _ Developing a Sampling Distribution (continued) (no longer uniform)

Summary Measures of this Sampling Distribution: Developing a Sampling Distribution (continued)

Comparing the Population with its Sampling Distribution 18 19 20 21 22 23 24 0 .1 .2 .3 P(x) x 18 20 22 24 A B C D 0 .1 .2 .3 Population N = 4 P(x) x _ Sample Means Distribution n = 2

If the Population is Normal (THEOREM 6-1) If a population is normal with mean μ and standard deviation σ, the sampling distribution of is also normally distributed with and

z-value for Sampling Distribution of x ,[object Object],where: = sample mean = population mean = population standard deviation n = sample size

Finite Population Correction ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Sampling Distribution Properties ,[object Object],Normal Population Distribution Normal Sampling Distribution (has the same mean)

Sampling Distribution Properties ,[object Object],[object Object],[object Object],Larger sample size Smaller sample size (continued)

If the Population is not Normal ,[object Object],[object Object],[object Object],[object Object],[object Object]

Central Limit Theorem n↑ As the sample size gets large enough… the sampling distribution becomes almost normal regardless of shape of population

If the Population is not Normal Population Distribution Sampling Distribution (becomes normal as n increases) Central Tendency Variation (Sampling with replacement) Larger sample size Smaller sample size (continued) Sampling distribution properties:

How Large is Large Enough? ,[object Object],[object Object],[object Object]

Example ,[object Object],[object Object]

Example ,[object Object],[object Object],[object Object],[object Object],[object Object],(continued)

Example ,[object Object],(continued) z 7.8 8.2 -0.4 0.4 Sampling Distribution Standard Normal Distribution .1554 +.1554 Population Distribution ? ? ? ? ? ? ? ? ? ? ? ? Sample Standardize

Population Proportions, p ,[object Object],[object Object],[object Object],[object Object],[object Object]

Sampling Distribution of p ,[object Object],[object Object],[object Object],(where p = population proportion) Sampling Distribution P( p ) .3 .2 .1 0 0 . 2 .4 .6 8 1 p

z-Value for Proportions ,[object Object],Standardize p to a z value with the formula:

Example ,[object Object],i.e.: if p = .4 and n = 200, what is P(.40 ≤ p ≤ .45) ?

Example ,[object Object],[object Object],(continued) Find : Convert to standard normal:

Example ,[object Object],[object Object],z .45 1.44 .4251 Standardize Sampling Distribution Standardized Normal Distribution (continued) Use standard normal table: P(0 ≤ z ≤ 1.44) = .4251 .40 0 p

Sampling distributions stat ppt @ bec doms

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