statistic homework

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Mathematics

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Name: class time: STP226 Group work#2 ch8. (10 points) Test scores of all students in Mat 142 classes have a normal distribution. The following is a random sample of 9 test scores from that population: 63, 71, 80, 66, 85,92, 56, 32, 77 a. (A points)Determine 95% confidence interval for u, the true mean test score of all Mat142 students (use t-interval procedure) b.(2 points) Based on the interval you obtained in part a, is it likely that is 86 or more? Explain your answer. Yes No (circle one) Reason: c. (2 point)Without computations determine if 99% CI based on your data will be narrower, wider, or the same width as your CI in part a. Narrower Wider The same width (circle one) d. (2 points) Suppose you computed 90% CI for u using a new sample of size 16. If the margin of of error in your CI was 12 points, what was a sample SD?
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Explanation & Answer

Hey buddy please find attached

Running Head: STP226

1

STP226
Name
Instructor
Course
Date

STP226

2

Part a
Confidence interval: ̅
X±t

s
√n

63+71+80+66+85+92+56+32+77
̅
X=
= 69.11
9

s=√

(63 − 69.11)2 + (71 − 69.11)2 + (80 − 69.11)2 + (66 − 69.11)2 + (85 − 69.11)2 + (92 − 69.11)2 + (56 − 69.11)2 + (32 − 69.11)2 + (77 − 69.11)2
9−1

s = 17.88
From the standard t-table;
t 0.05 = 1.860
Confidence interval = 69.11 ± (1.860 ×

17.88
√9

) = 69.11 ± 11.09

Confidence interval = 58.02 ≤ μ ≤ 80.2
Part b
No
Because the upper limit of the interval (80.2) is less t...


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