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s344n2d4d5 [400]
3 years ago
10

Past experience has indicated that the breaking strength of yarn used in manufacturing drapery material is normally distributed.

A random sample of 8 specimens is tested, and the breaking strength for each specimen is recorded. Assuming known population standard deviation, the width of a 95 percent confidence interval was found to be 2.694. What was the value of population standard deviation used in calculating the confidence interval?
Mathematics
1 answer:
OLEGan [10]3 years ago
3 0

Answer: the value of population standard deviation is 3.87

Step-by-step explanation:

From the information given,

Number of sample, n = 8

For a confidence level of 95%, the corresponding z value is 1.96. This is determined from the normal distribution table.

We will apply the formula

Confidence interval

= mean ± z ×standard deviation/√n

Since confidence interval = 2.694,

It becomes

2.694 = 1.96 × standard deviation/√8

Dividing both sides of the equation by 1.96, it becomes

1.37 = standard deviation/√8

Standard deviation = 1.37 × √8

Standard deviation = 3.87

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The points , (−15,1) and , (−7,r) lie on a line with slope 5/4. Find the missing coordinate r. Click image to enlarge
Nadya [2.5K]

The missing coordinate r is 11.

Solution:

Given points are (–15, 1) and (–7, r).

x_{1}=-15, x_{2}=-7, y_{1}=1 \text { and } y_{2}=7

Slope (m) = \frac{5}{4}

<u>To find the missing coordinate r:</u>

Slope formula:

$m=\frac{y_{2}-y_{1}}{x_{2}-x_{1}}$

Substitute the given values in the formula.

$\frac{5}{4}=\frac{r-1}{-7-(-15)}

$\frac{5}{4}=\frac{r-1}{-7+15}

$\frac{5}{4}=\frac{r-1}{8}

Do cross multiplication.

8 \times 5=4(r-1)

40 = 4r – 4

Add 4 on both side of the equation.

44 = 4r

Divide by 4 on both side of the equation.

11 = r

⇒ r = 11

Hence the missing coordinate r is 11.

6 0
3 years ago
What’s the answer pleazzzzz helplllllll 9m^2-4m-6 by 3m
dlinn [17]

Answer

D. 3m - 4/3 -2/m


<u>Explanation</u>

(9m²-4m-6) ÷ 3m  = 9m²/3m - 4m/3m - 6/3m

Carry out the division, each term is divided by 3m.

9m²/3m = 3m

- 4m/3m = -4/3

- 6/3m = - 2/m

Finally you will get,

<em>3m - 4/3 -2/m</em>

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Mary went on vacation from the uk to the us, so she had to purchase some dollars ($). how many pounds sterling (l) did she excha
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Exchange rate L 1 = $ 1.5542

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3 years ago
Final exam scores are normally distributed with a mean of 74 and a standard deviation of 6. Approximately, what percentage of fi
notka56 [123]

Answer:

81.86%

Step-by-step explanation:

We have been given that final exam scores are normally distributed with a mean of 74 and a standard deviation of 6.

First of all we will find z-score using z-score formula.

z=\frac{x-\mu}{\sigma}

z=\frac{68-74}{6}

z=\frac{-6}{6}=-1

Now let us find z-score for 86.

z=\frac{86-74}{6}    

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Now we will find P(-1<Z) which is probability that a random score would be greater than 68. We will find P(2>Z) which is probability that a random score would be less than 86.

Using normal distribution table we will get,    

P(-1

P(2>Z)=.97725  

We will use formula P(a to find the probability to find that a normal variable lies between two values.

Upon substituting our given values in above formula we will get,

P(-1

P(-1

Upon converting 0.81859 to percentage we will get

0.81859*100=81.859\approx 81.86

Therefore, 81.86% of final exam score will be between 68 and 86.  


3 0
3 years ago
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