Help me with this question please

A sample of n = 4 scores is obtained from a population with a mean of 70 and a standard deviation of 8. If the sample mean corre

jeka57 [31]

Answer:

The value of the sample mean is 78.

Step-by-step explanation:

We are given that a sample of n = 4 scores is obtained from a population with a mean of 70 and a standard deviation of 8.

Also, the sample mean corresponds to a z score of 2.00.

Let $\bar X$ = sample mean

The z-score probability distribution for a sample mean is given by;

Z = $\frac{\bar X-\mu}{\frac{\sigma}{\sqrt{n} } }$ ~ N(0,1)

where, $\mu$ = population mean = 70

$\sigma$ = standard deviation = 8

n = sample size = 4

The Z-score measures how many standard deviations the measure is away from the mean. After finding the Z-score, we look at the z-score table and find the p-value (area) associated with this z-score. This p-value is the probability that the value of the measure is smaller than X, that is, the percentile of X.

Now, we are given that the sample mean corresponds to a z score of 2.00 for which we have to find the value of sample mean;

So, z-score formula is given by ;

z-score = $\frac{\bar X-\mu}{\frac{\sigma}{\sqrt{n} } }$ = $\frac{\bar X-70}{\frac{8}{\sqrt{4} } }$

2.00 = $\frac{\bar X-70}{\frac{8}{\sqrt{4} } }$

2.00 = $\frac{\bar X-70}{4 } }$

$\bar X = 70+(2 \times 4)$

$\bar X$ = 70 + 8 = 78

Therefore, the value of the sample mean is 78.

3 0

3 years ago

1..A message in a bottle is floating on top of the ocean in a periodic manner. The time between periods of maximum heights is 26

statuscvo [17]

Answer:

See below for answers and explanations (along with a graph attached)

Step-by-step explanation:

Part A

The amplitude of a sinusoidal function is half the distance between the maximum and the minimum. It is given to us that the distance from the highest and lowest point is 6 feet, so our amplitude is 6/2 = 3 feet

Part B

The graph's function would be in the form of $y=acos(bx+c)+d$ where $a$ is the amplitude, $\frac{2\pi}{b}$ is the period, $-\frac{c}{b}$ is the phase/horizontal shift, and $d$ is the average/midline.

We already know our amplitude of $a=3$ from part A.

Since our period is given to us as 26 seconds, then we can use the equation $\frac{2\pi}{b}=26$ to find $b$ , which happens to be $b=\frac{\pi}{13}$ .

Since the cosine function starts at its maximum and we want it to start at the average where the bottle travels up, we would need to use the cofunction identity $sin(x)=cos(x-\frac{\pi}{2})$ which shifts the cosine graph $\frac{\pi}{2}$ units to the right. This means that $c=-\frac{\pi}{2}$ , making our phase shift $-\frac{c}{b}=-\frac{-\frac{\pi}{2}}{\frac{\pi}{13}}=6.5$ , or 6.5 feet to the right

Our average/midline would be $d=12$ as given as the average height by the problem.

Therefore, the function is $f(x)=3cos(\frac{\pi}{13}x-\frac{\pi}{2})+12$

Part C

Using our determined function from Part B, by looking at its graph, we see that the bottle will reach its lowest height of 9 feet after 19.5 seconds (see attached graph).

5 0

2 years ago

Read 2 more answers

If you multiply this number by 3 , then subtract 15 , the result is 51. What is the number?

bagirrra123 [75]

3x-15=51 3x=36 X= 12 Thus the number is 12

8 0

3 years ago

Please help this is urgent

lys-0071 [83]

Answer:

the common factor is: X - 4.

Step-by-step explanation:

( x-4 ) is what the numerator and the denominator have in common.

3 0

3 years ago

at a movie theater, the size of popcorn bags decreased 20% . if the old bags held 15 cups of popcorn, how much do the new bags h

Lilit [14]

Answer:

12 cups

Step-by-step explanation:

If the size of the bag decreased by 20%, so will the number of cups held.

Number of cups held before the change = 15 cups

If the number of cups held after the 20% reduction in the size of the bag

= (100 - 20)% × 15

=80% × 15

= 12 cups

The new bags will hold 12 cups.

8 0

3 years ago