外教期末

5.25

Welcome!

Default homework due date = one week

SO NEW HOMEWORK:

due Monday, May 25:

chapter 3, problem 2a,b, c,d [one sided, lower confidence] chapter 3, problem 8abc

more problems TBA [to be announced!]

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PLAN:

final exam ~June 12

THIS WEEK:

chapter 3, 4

next week: chapters 4,5

Week 6: chapter 14

inference process:

0. calculate xbar and maybe sigma from some data

1. make our inference

2. calculate a test statistic

3. look up on the Normal table

4. make a decision [yes or no!]

H1

two-side ==== is not equals to

one sided ===== either < or >

one sided: mean exceeds or is greater than hypothesis testing process

[we are making an inference!]

3-1 in your book, page 139

1. write the hypotheses

Ho: u = 8.25 cm

H1: u is NOT equal to 8.25

2. if you know sigma,

use Zo=6.7777, page 98

3. we need to look up

on the normal table to see what the normal

distribution says.

it depends on alpha

alpha = producer's risk = the uncertainty,

Uncertainty that we reject Ho and Ho is true

alpha is usually small, usually like 0.01 or 0.05

AGAIN, your producer [ie. your boss] will know

this

4 options:

1. we say Ho is true and it really IS true :)... we are correct

2. we say Ho is false and it really IS false :)... we are correct

3. we might say Ho is false and it is really TRUE = producer's error [we wish this = 0, but its a small number: 0.001, 0.01, 0.05... producer has the 'problem'

you are fixing something is OK.

example: you are working on the midterm....

you take a look at your answers.....

you take a second look, one answer looks 'funny' and you change it. unfortunately, you change it and make it wrong. it was right in the first place!!

alpha = producer knows = producer error = type 1 error

4. we might say Ho is true and it is FALSE = consumer's error

like SanLu milk, they thought its ok and its NOT.

the consumer gets harmed

BETA error = type 2 error = we don't want to estimate

4

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3-2

1. write the hypotheses Ho: u= 125

H1: u > 125

2

3

4

--------------

1. write the hypotheses Ho:

H1:

2

3

3-1 in your book, page 139 1. write the hypotheses Ho: u = 8.25 cm

H1: u is NOT equal to 8.25

2. if you know sigma,

use Zo=6.7777, page 98

3. look up Z[table]

*decide what is alpha = 0.05

*decide is it alpha or alpha/2

use alpha/2 if NOT EQUALS TO

use alpha if > or <

process: look up what is 1 - alpha/2 = 1 - 0.05/2 = 1 - 0.025 = phi = 0.975, what was Z[table]??

from the normal tables..... page 716 and 717....

Z[table] = 1.96

review hypothesis process:

1. write hypotheses

2. calculate Zo

3. find Z[table]

4. decision rule on page 98