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Practice. 8.17. 8.17. 110 or greater Z = 105-100/3 = 1.67 p = .0475 90 or less Z = 90-100/3 = -3.33 p = .0004. Practice. For an SAT test  = 500  = 100 What is the probability that a sample of 65 people will have a mean SAT score below 525?. Step 1: Sketch out question.

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Practice

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• 8.17

### 8.17

• 110 or greater

• Z = 105-100/3 = 1.67

p = .0475

• 90 or less

• Z = 90-100/3 = -3.33

p = .0004

### Practice

• For an SAT test

•  = 500

•  = 100

• What is the probability that a sample of 65 people will have a mean SAT score below 525?

-3 -2 -1 012 3

100 / 65 = 12.40

-3 -2 -1 012 3

### Step 3: Calculate the Z score

(525 - 500) / 12.40 = 2.02

-3 -2 -1 012 3

### Step 4: Look up Z score in Table

Z = 2.02; Column B =.4783

.50

.4783

-3 -2 -1 012 3

### Practice

• There is a .9783 probability that a sample of 65 people would have a mean SAT under 525

### Practice

• In a large corporation, the mean salary for all males with 3 to 5 years of experience was \$28,000. Salaries (expressed in thousands) for a random sample of 10 women also having 3 to 5 years of experience were:

• 24, 27, 31, 21, 19, 26, 30, 22, 15, 36

• Construct the 95% confidence interval for women and interpret what this means relative to the mean salary of males.

### Practice

• M = 25.1

• SE = 1.97

• t(9) = 2.262

• 20.64 to 29.56

• 20,640 to 29,560

8.30

### Practice

• SE = 1.0

• t = 2.064

• T1 = 5.936 to 10.064

• T2 = 3.936 to 8.064

• T3 = 11.936 to 16.064

• T4 = 13.936 to 18.064

8.23

### Practice

• M= 27

• S hat = 3.803

• SE = 1.016

• t (13)= 2.160

• LL = 24.8

• UL = 29.2

• The workshop is working. We are 95% confident the average score of everyone who takes the workshop would be above 24 (the norm of the test)

### Practice

• 8.12

• 8.13

As N (sample size) increases the standard error decreases!

### Cookbook

• Bring your cookbook to class on Friday!