Question

Chapter 6, Section 4-CI, Exercise 188:

A 95% confidence interval for U1 - U2 using the sample results Xbar 1 = 80.7, S1=9.2, N1=35 and Xbar 2 = 63.0, S2=8.0, N2=20 .

Best estimate:

Margin of error (two decimal places):

Confidence Error (two decimal places):

Answer 1

Best estimate = (80.7-63.0)

= 17.7

Margin of error

degree of freedom df = (n1+n2)-2 = (35+20)-2 = 53

the value of 95% confidence from t table with df is t = 2.006

margin of error formula

=> t * sqrt(s1^2/n1 + s2^2/n2)

=> 2.006 * sqrt((9.2^2/35) + (8.0^2/20))

=> 4.7548

confidence interval

Best estimate +/- margin of error

=> 17.7+/- 4.7548

=> (12.9452 to 22.4548)

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