Mth 139 Quiz See 61-63 Directions: Circle the correct response. 1. Given the sam

Question

Mth 139 Quiz See 61-63 Directions: Circle the correct response. 1. Given the same sample statistics, which level of confidence will produce the narrowest confidence interval? a) 75% b) 85% c) 95% d)90% 2. What is the effect on the width of the confidence interval if the sample size is increased from 20 to 100? a) The width decreases b) The width increases c) The width remains the same. d) It is impossible to tell without more information 3. Find the critical value, z, for c-94 a) 1.96 6 1.88 c) 2.05 d) 2.33 4. A random sample of 40 students has an average test score of 81.5. Assume the population standard deviation is 10.2. Construct a 90% confidence interval for the population mean. a) (71.8

Explanation / Answer

1) option A is correct being lowest

2) option a

3) option b

4)for std error =std deviation/(n)1/2 =1.613

hence confidence interval =sample mean -/+ z*std error =78.8 ; 84.2

option B

5)

sample size n=(z*std deviaiton/E)2 =(1.645*9/3)2 =25

option B

6) option B

7)

option b is correct

8)p=347/2070

option B

9)

option b

10)

sample size n=p(1-p)*(Z/E)2 =~999

option D

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