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Ganezh [65]
3 years ago
6

The minimal Brinell hardness for a specific grade of ductile iron is 130. An engineer has a sample of 25 pieces of this type of

iron that was subcritically annealed with the Brinell hardness values as given below. The engineer would like to know whether this annealing process results in the proper Brinell hardness on average.
135 149 132 142 124 130 122 128 120 128 127 123 136 141 130 139 134 135 130 141 149 137 137 140 148

State the appropriate hypotheses; conduct a hypothesis test using α = 0.05 utilizing the classical approach, confidence interval approach, or p-value approach; state the decision regarding the hypotheses; and make a conclusion.
Mathematics
1 answer:
docker41 [41]3 years ago
3 0

Answer:

t=\frac{134.28-130}{\frac{8.229}{\sqrt{25}}}=2.60  

Critical value

df=n-1=25-1=24  

We need to find a critical value in the t distribution with df=29 who accumulates 0.025 of the area on each tail and we got:

t_{\alpha/2} = \pm 2.06

Since our calculated value is higher than the critical value we have enough evidence to reject the null hypothesis at 5% of significance

P-value  

Since is a two-sided tailed test the p value would given by:  

p_v =2*P(t_{(24)}>2.60)=0.0157  

Conclusion  

If we compare the p value and the significance level given \alpha=0.05 we see that p_v so we can conclude that we have enough evidence to to reject the null hypothesis and we can say that the true mean is not equal to 130 the specification.  

Step-by-step explanation:

Data given and notation  

135 149 132 142 124 130 122 128 120 128 127 123 136 141 130 139 134 135 130 141 149 137 137 140 148

We can calculate the mean with the following formula:

\bar X = \frac{\sum_{i=1}^n X_i}{n}

And the deviation with:

s= \frac{\sum_{i=1}^n (X_i -\bar X)^2}{n-1}

\bar X=134.28 represent the sample mean  

s=8.229 represent the sample standard deviation  

n=25 sample size  

\mu_o =130 represent the value that we want to test  

\alpha=0.05 represent the significance level for the hypothesis test.  

t would represent the statistic (variable of interest)  

p_v represent the p value for the test (variable of interest)  

State the null and alternative hypotheses.  

We need to conduct a hypothesis in order to check if the true mean is equal to 130 :  

Null hypothesis:\mu = 130  

Alternative hypothesis:\mu \neq 130  

Since we don't know the population deviation, is better apply a t test to compare the actual mean to the reference value, and the statistic is given by:  

t=\frac{\bar X-\mu_o}{\frac{s}{\sqrt{n}}} (1)  

t-test: "Is used to compare group means. Is one of the most common tests and is used to determine if the mean is (higher, less or not equal) to an specified value".  

Calculate the statistic  

We can replace in formula (1) the info given like this:  

t=\frac{134.28-130}{\frac{8.229}{\sqrt{25}}}=2.60  

Critical value

We need to calculate the degrees of freedom first given by:  

df=n-1=25-1=24  

We need to find a critical value in the t distribution with df=29 who accumulates 0.025 of the area on each tail and we got:

t_{\alpha/2} = \pm 2.06

Since our calculated value is higher than the critical value we have enough evidence to reject the null hypothesis at 5% of significance

P-value  

Since is a two-sided tailed test the p value would given by:  

p_v =2*P(t_{(24)}>2.60)=0.0157  

Conclusion  

If we compare the p value and the significance level given \alpha=0.05 we see that p_v so we can conclude that we have enough evidence to to reject the null hypothesis and we can say that the true mean is not equal to 130 the specification.  

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Answer:

j=12

Step-by-step explanation:

we know that

In a join variation, If j varies jointly with respect to g and v, the equation will be of the form j = kgv

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substitute and solve for k

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The equation is equal to

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step 2

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3 years ago
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GREYUIT [131]

Answer:

The monthly compounded interest rate of 0.14% of Unity Bank is a better plan.

Step-by-step explanation:

<em>Step 1 : Write the formula for calculating a monthly compound interest rate and for calculating an annually compounded interest rate.</em>

Monthly compound interest rate = P(1+r/n)^nxt

<em>n=12 (number of months in a year)</em>

<em>t=1 (number of years)</em>

Annually compound interest rate = P(1+r/n)^nxt

<em>n=1 (because it is for 1 year only)</em>

<em>t=1 (number of years=1)</em>

<em>Step 2 : Lets assume that P is $100 in both banks and time is 1 year.</em>

<em>Step 3 : Lets substitute the values to find out which one is better.</em>

Monthly compound interest rate = P(1+r/n)^nxt

Monthly compound interest rate = 100(1+0.14/12)^12x1

Monthly compound interest rate = 114.93

114.93 - 100 = $14.93 per month

14.93 x 12 = $179.16 for 12 months or 1 year

Annually compound interest rate = P(1+r/n)^nxt

Annually compound interest rate = 100(1+1.6/1)^1x1

Annually compound interest rate = 260

260-100 = $160 for 1 year

Therefore, the monthly compounded interest rate of 0.14% of Unity Bank is a better plan.

!!

8 0
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emmasim [6.3K]
I believe the answer is $45.75.
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