practice questions for Test3_solutions

# practice questions for Test3_solutions - Solutions to...

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Solutions to PRETEST 3. TEST 3 will be given on Wednesday December 3 I-1. We decrease the width of the confidence interval by (1) increasing sample size(2) decreasing the confidence value and (3) decreasing the standard deviation of the variable. So to increase the width of the confidence interval we would decrease sample size or increase the confidence value or increase the standard deviation. I-2. Pr (t > t 0.01 )= 0.01 = Pr(t< -t 0.01 ). I-3. This is a one sided test to the left at the 0.01 level with n large. So the rejection region is z < -z α . Here α =0.01, z 0.01 =2.33 and the rejection region is z<-2.33.(c) I-4. The probability he accepts Ho if Ho is not true β ( μ ) decreases as | μ - μ 0 | increases. Thus since |15-10| > |14-10|, β (15)< β (14)=0.5. FALSE I-5. If μ =10 then the null hypothesis is true and if the investigator rejects Ho he is WRONG. TRUE I-6. t=-2.0 then |t| = 2.0. Since 2.0<3.18 we can not reject Ho at the 0.05 level and we conclude that μ =48mm. I-7. The 95% confidence interval contains all μ we can not reject at the 0.05 level two sided. The value 88 is on the 95% confidence interval

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