Answer:
The 95% confidence interval for the concentration in whitefish found in Yellowknife Bay is (0.2698 mg/kg, 0.3702 mg/kg).
Step-by-step explanation:
We have the standard deviation for the sample, which means that the t-distribution is used to solve this question.
The first step to solve this problem is finding how many degrees of freedom, we have. This is the sample size subtracted by 1. So
df = 8 - 1 = 7
95% confidence interval
Now, we have to find a value of T, which is found looking at the t table, with 7 degrees of freedom(y-axis) and a confidence level of
. So we have T = 2.3246
The margin of error is:

In which s is the standard deviation of the sample and n is the size of the sample.
The lower end of the interval is the sample mean subtracted by M. So it is 0.32 - 0.0502 = 0.2698 mg/kg
The upper end of the interval is the sample mean added to M. So it is 0.32 + 0.0502 = 0.3702 mg/kg
The 95% confidence interval for the concentration in whitefish found in Yellowknife Bay is (0.2698 mg/kg, 0.3702 mg/kg).
Answer:
15
Step-by-step explanation:
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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.