Mathematics, 02.07.2020 23:01 emilyscroggins794

A sample of 50 cotton threads shows the mean breaking strength to be 220 grams and the sample standard deviation to be 12 grams. What is the 95% confidence interval for the standard deviation of breaking strength of the thread.

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Answer from: zdwilliams1308

$220-2.01\frac{12}{\sqrt{50}}=216.589$

$220+2.01\frac{12}{\sqrt{50}}=223.411$

The confidence interval for this case would be (216.589, 223.411)

Step-by-step explanation:

Information given

$\bar X=220$ represent the sample mean

$\mu$ population mean

s=12 represent the sample standard deviation

n=50 represent the sample size

Confidence interval

The confidence interval for the mean is given by the following formula:

$\bar X \pm t_{\alpha/2}\frac{s}{\sqrt{n}}$ (1)

The degrees of freedom are given by:

df=n-1=50-1=49

The Confidence level is 0.95 or 95%, the significance is $\alpha=0.05$ and $\alpha/2 =0.025$ , the critical value for this case is $t_{\alpha/2}=2.01$

And replacing we got:

$220-2.01\frac{12}{\sqrt{50}}=216.589$

$220+2.01\frac{12}{\sqrt{50}}=223.411$

The confidence interval for this case would be (216.589, 223.411)

Answer from: Quest

answer:

payment just for service

→

87.12

payment for service including tax

→

94.09

explanation:

service only with 20% tip

→

72.6

(

100

)

87.12

in the opening of the question the word 'service' is associated only with the pretax value.

the closing part of the question asks: how much did she pay for the

service

−−−−−−

so technically the answer is

→

72.6

(

100

)

87.12

however, the intention of the question provider may have been that your answer is to be

87.12

(

100

)

94.09

to 2 decimal places.

payment just for service

→

87.12

payment for service including tax

→

94.09

tony b

mar 21, 2017

answer:

trying to explain it another way

explanation:

service charge

→

72.60

20% tip

100

72.60

14.52

−−−−−−

←

add

87.12

tax

100

87.12

6.97

−−−−−

←

add

94.09

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