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Engineering

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On questions requiring a numerical answer, show how the answer was obtained, by
attaching Excel files, and a copy of your manual calculations on words
Exercise 4-72 on page 214
Consider the Minitab output shown below, which also includes a Z-value = 2.76 and a
P-value = 0.006.
(a) Is this a one-sided or a two-sided test?
This is a two-sided test because you will look at areas above and below p=0.3.
(b) Was this test conducted using the normal approximation to the binomial? Was that
appropriate? The normal approximation to the binomial was used. It is
appropriate because Np and N(1-p) are 95 and 155 respectively. 95 and 155
are both greater than 5 so a normal approximation can be used.
(c) Can the null hypothesis be rejected at the 0.05 level? The null hypothesis would
be rejected because the p-value 0.006 is less than 0.05.
(d) Can the null hypothesis
 versus
 be rejected at the 0.05 level?
How can you do this without performing any additional calculations? No, it cannot
be rejected. You can tell by looking at the 95% confidence interval. Since 0.4
is within the interval range, the p-value would still be too large to reject.

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(e) Construct an approximate 90% traditional CI for p.
First, find the z-scores for the normal that would give you 5% to the left
(outside area of confidence interval is divided evenly between the left and right
side.) Excel was used to find a z-score or -1.6448536 for the lower bound.
Because the interval will be symmetrical on both sides of the normal curve, the
upper bound z-score is 1.6448536. The standard deviation can be calculated
using the formula



0.03069853.
To find CI:

  
Lower bound: -1.6448536(0.0306985) +0.38 = 0.3295054
Upper bound: 1.6448536(0.0306985) +0.38 = 0.4304946
So, the 90% confidence interval for p is:

Exercise 4-73 on page 214
Consider the following Minitab output.
Test and CI for One Proportion
Test of 
Sample X N Sample p 95% Lower Z-value P-value
Bound
1 553 800 ? ? 2.45 ?
(a) Is this a one-sided or a two-sided test?
This is a one-sided test because we are only concerned about the area to the right
of p
(b) Was this test conducted using the normal approximation to the binomial? Was that
appropriate? Yes, the test was used using the normal approximation to the binomial.
This is appropriate because the number of times the event occurred is 553 which
is greater than 5 and the number of times the event did not occur is 247 which is
also greater than 5.
(c) Fill in the missing values.
Sample p =


0.69125

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• On questions requiring a numerical answer, show how the answer was obtained, by attaching Excel files, and a copy of your manual calculations on words Exercise 4-72 on page 214 Consider the Minitab output shown below, which also includes a Z-value = 2.76 and a P-value = 0.006. (a) Is this a one-sided or a two-sided test? This is a two-sided test because you will look at areas above and below p=0.3. (b) Was this test conducted using the normal approximation to the binomial? Was that appropriate? The normal approximation to the binomial was used. It is appropriate because Np and N(1-p) are 95 and 155 respectively. 95 and 155 are both greater than 5 so a normal approximation can be used. (c) Can the null hypothesis be rejected at the 0.05 level? The null hypothesis would be rejected because the p-value 0.006 is less than 0.05. (d) Can the null hypothesis 𝐻0 : 𝑝 = 0.4 versus 𝐻1 : 𝑝 ≠ 0.4 be rejected at the 0.05 level? How can you do this without performing any additional calculations? No, it cannot be rejected. You can tell by looking at the 95% confidence interval. Since 0.4 is within the interval range, the p-value would still be too large to reject. (e) Construct an approximate 90% traditional CI for p. First, find the z-scores for the normal that would give you 5% to the left (outside area of confidence interval is divided evenly between the left and right side.) Excel was used to find a z-score or -1.6448536 for the lower bound. Because the interval wi ...
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