20

Jack is a college athlete who has been weighing himself weekly on the same scale in the athletic center for the past few years.

Radda [10]

Answer:

a) Since the Confidence is 0.90 or 90%, the value of $\alpha=0.1$ and $\alpha/2 =0.05$ , and we can use excel, a calculator or a table to find the critical value. The excel command would be: "=-NORM.INV(0.05,0,1)".And we see that $z_{\alpha/2}=\pm 1.64$

b) $\bar X \sim N(\mu ,\frac{\sigma}{\sqrt{n}})$

And the standard error is given by:

$SE = \frac{\sigma}{\sqrt{n}}=\frac{3}{\sqrt{9}}=1$

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

And the margin of error is:

$ME= z_{\alpha/2} \frac{\sigma}{\sqrt{n}} = 1.64$

And then the confidence interval is be given by:

$200-1.64 = 198.36$

$200+1.64 = 201.64$

Step-by-step explanation:

Previous concepts

A confidence interval is "a range of values that’s likely to include a population value with a certain degree of confidence. It is often expressed a % whereby a population means lies between an upper and lower interval".

The margin of error is the range of values below and above the sample statistic in a confidence interval.

Normal distribution, is a "probability distribution that is symmetric about the mean, showing that data near the mean are more frequent in occurrence than data far from the mean".

$\bar X= 200$ represent the sample mean

$\mu$ population mean (variable of interest)

$\sigma=3$ represent the population standard deviation

n=9 represent the sample size

Part a

Since the Confidence is 0.90 or 90%, the value of $\alpha=0.1$ and $\alpha/2 =0.05$ , and we can use excel, a calculator or a table to find the critical value. The excel command would be: "=-NORM.INV(0.05,0,1)".And we see that $z_{\alpha/2}=\pm 1.64$

Part b

The distribution for the sample mean is given by:

$\bar X \sim N(\mu ,\frac{\sigma}{\sqrt{n}})$

And the standard error is given by:

$SE = \frac{\sigma}{\sqrt{n}}=\frac{3}{\sqrt{9}}=1$

Part c

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

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

And the margin of error is:

$ME= z_{\alpha/2} \frac{\sigma}{\sqrt{n}} = 1.64$

And then the confidence interval is be given by:

$200-1.64 = 198.36$

$200+1.64 = 201.64$

8 0

2 years ago

Please please please help me

Zinaida [17]

Answer:

z=20 and y=38

Step-by-step explanation:

6 0

2 years ago

Help me …… please ! I Just need help

frozen [14]

Answer:

(2,-2)

Step-by-step explanation:

y=-4x+6

y=3x-8

plug the y's in for each other to get:

-4x+6=3x-8 <----- solve from there

+8 +8

-4x+14=3x

+4x +4x

14=7x

/7 /7

x=2

now plug the x in to get y (in any problem)

y=3(2)-8

y=6-8

y=-2

7 0

2 years ago

Becca and Kimberly are running at a constant speed in a marathon. Becca runs at 4.5 miles per hour. Kimberly’s progress is shown

Georgia [21]

Answer:

Part A: Kimberly

Part B:

Becca = 22.5 miles, Kimberly = 25 miles

Step-by-step explanation:

Part A:

Given that Becca runs at a constant speed of 4.5 miles per hour, use the table to find the constant speed that Kimberly runs, and compare who runs faster.

Let x = time

y = distance

k = speed = y/x

Equation for each person can be written as: y = kx

Therefore:

✔️Equation for Becca if k = 4.5

y = 4.5x

✔️Find k (speed) of Kimberly using (2, 10):

Speed (k) = y/x

k = 10/2

k = 5 miles per hour

Equation for Kimberly would be:

y = 5x

Comparing their speed, Kimberly runs faster because she covers more miles per hour than Becca does.

Part B:

For Becca, substitute x = 5 into Becca's equation, y = 4.5x

Thus:

y = 4.5*5 = 22.5 miles

For Kimberly, substitute x = 5 into Kimberly's equation, y = 5x

Thus:

y = 5*5 = 25 miles

5 0

2 years ago

Please help me

nikklg [1K]

Answer:

2. $1,100 in clothing sales gives Rachel a $260 paycheck

3 $.2,200 in clothing sales gives Rachel a $370 paycheck

5. $10,800 in clothing sales gives Rachel a 1,230 paycheck

Step-by-step explanation:

Here is the complete question :

Rachel works for a clothing store. She is $150 paid every week plus a 10% commission on any clothes that she sells. Which of the following is true in regards to Rachel's weekly paycheck? Chose three correct answers.

1. $100 in clothing sales gives Rachel a $250 paycheck

2. $1,100 in clothing sales gives Rachel a $260 paycheck

3 $.2,200 in clothing sales gives Rachel a $370 paycheck

4. $ 4,200 in clothing sales gives Rachel a $420 paycheck

5. $10,800 in clothing sales gives Rachel a 1,230 paycheck

6. $ 16,000 in clothing sales gives Rachel a 1,450 paycheck

The equation representing Rachel's paycheck = amount she earns every month + commission

If she makes $100 in clothing sales, her paycheck = $150 + (0.1 x 100) = $160

If she makes $1100 in clothing sales, her paycheck = $150 + (0.1 x 1100) = $260

If she makes $2200 in clothing sales, her paycheck = $150 + (0.1 x 2200) = $370

If she makes $4200 in clothing sales, her paycheck = $150 + (0.1 x 4200) = $570

If she makes $10800 in clothing sales, her paycheck = $150 + (0.1 x 10800) = $1230

If she makes $16000 in clothing sales, her paycheck = $150 + (0.1 x 16000) = $1750

thus the correct options are 2,3,5

4 0

2 years ago