The time, T (seconds) it takes for a pot of
1 answer:
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Answer:
Explained below.
Step-by-step explanation:
(1)
The hypothesis can be defined as follows:
<em>H</em>₀: The Speedy Oil Change will change the oil in customers’ cars in more than 30 minutes on average, i.e. <em>μ</em> > 30.
<em>H</em>ₐ: The Speedy Oil Change will change the oil in customers’ cars in less than 30 minutes on average, i.e. <em>μ</em> ≤ 30.
(2)
Use Excel to compute the sample mean and standard deviation as follows:
Compute the test statistic as follows:
The degrees of freedom is:
df = n - 1
= 36 - 1
= 35
Compute the p-value as follows:
(3)
The <em>p</em>-value = 0.0006 is very small.
The null hypothesis will be rejected at any of the commonly used significance level.
(4)
There is sufficient evidence to support the claim that the Speedy Oil Change will change the oil in customers’ cars in less than 30 minutes on average.
Answer: 169.2 per acre are produced if a field is in the top 25%.
Step-by-step explanation:
Given: The mean rain-fed corn yield of harvested fields are normally distributed, produce 147.2 bushels per acre with a standard deviation of 33 bushels per acre.
Let X denote the mean rain-fed corn yield of harvested fields.
Let x denotes the number of bushels per acre are produced if a field is in the top 25%.
Top 25% on a density curve means , (100-25%)i.e. 75% area lies below x.
I.e.
.
Z-score for p-value of 0.75 (one tailed)=0.67 [By z-table]
Then,
Here approx value is 169.2 (from options).
So, 169.2 per acre are produced if a field is in the top 25%.