(a)
To test: Whether there is any statistically significant evidence at the
(a)
Answer to Problem 17.38E
There is statistically significant difference at
Explanation of Solution
Given info:
The data represents the sample of strength of pieces of wood and standard deviation 3,000 pounds.
Calculation:
STATE:
The strength of pieces of wood follows
PLAN:
Parameter:
Define the parameter
The hypotheses are given below:
The claim of the problem is the mean strength is different from 32,500.
Null Hypothesis:
That is, the mean strength is equal to 32,500.
Alternative hypothesis:
That is, the mean strength is not equal to 32,500.
SOLVE:
Conditions for valid test:
A sample of 20 pieces of wood is randomly selected and strength of pieces of wood follows normal distribution with standard deviation
Test statistic and P-value:
Software procedure:
Step-by-step procedure to obtain test statistic and P-value using the MINITAB software:
- Choose Stat > Basic Statistics > 1-Sample Z.
- In Samples in Column, enter the column of Strength of pieces.
- In Standard deviation, enter 3,000.
- In Perform hypothesis test, enter the test mean as 32,500.
- Check Options, enter Confidence level as 90.
- Choose not equal in alternative.
- Click OK in all dialogue boxes.
Output using the MINITAB software is given below:
From the MINITAB output, the test statistic is –2.47 and the P-value is 0.013.
Decision criteria for the P-value method:
If
If
CONCLUDE:
Use a significance level,
Here, P-value is 0.013, which is lesser than the value of
That is,
Therefore, the null hypothesis is rejected.
Thus, there is statistically significant at
(b)
To test: Whether there is any statistically significant evidence at the
(b)
Answer to Problem 17.38E
There is no statistically significant difference at
Explanation of Solution
Calculation:
STATE:
Is there statistically significant evidence at the
PLAN:
Parameter:
Define the parameter
The hypotheses are given below:
The claim of the problem is the mean strength is different from 31,500.
Null Hypothesis:
That is, the mean strength is equal to 31,500.
Alternative hypothesis:
That is, the mean strength is not equal to 31,500.
SOLVE:
Conditions for valid test:
A sample of 20 pieces of wood is randomly selected and strength of pieces of wood follows normal distribution with standard deviation
Test statistic and P-value:
Software procedure:
Step-by-step procedure to obtain test statistic and P-value using the MINITAB software:
- Choose Stat > Basic Statistics > 1-Sample Z.
- In Samples in Column, enter the column of Strength of pieces.
- In Standard deviation, enter 3,000.
- In Perform hypothesis test, enter the test mean as 31,500.
- Check Options, enter Confidence level as 90.
- Choose not equal in alternative.
- Click OK in all dialogue boxes.
Output using the MINITAB software is given below:
From the MINITAB output, the test statistic is –0.98 and the P-value is 0.326.
CONCLUDE:
Use a significance level,
Here, P-value is 0.326, which is greater than the value of
That is,
Therefore, the null hypothesis is not rejected.
Thus, there is no statistically significant difference at
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Chapter 17 Solutions
The Basic Practice of Statistics
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