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A simple random sample of size nequals81 is obtained from a population with mu equals 83 and sigma equals 27. (a) Describe the

Ivanshal [37]

Answer:

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

With:

$\mu_{\bar X}= 83$

$\sigma_{\bar X}=\frac{27}{\sqrt{81}}= 3$

b) $z= \frac{89-83}{\frac{27}{\sqrt{81}}}= 2$

$P(Z>2) = 1-P(Z$

c) $z= \frac{75.65-83}{\frac{27}{\sqrt{81}}}= -2.45$

$P(Z$

d) $z= \frac{89.3-83}{\frac{27}{\sqrt{81}}}= 2.1$

$z= \frac{79.4-83}{\frac{27}{\sqrt{81}}}= -1.2$

$P(-1.2$

Step-by-step explanation:

For this case we know the following propoertis for the random variable X

$\mu = 83, \sigma = 27$

We select a sample size of n = 81

Part a

Since the sample size is large enough we can use the central limit distribution and the distribution for the sampel mean on this case would be:

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

With:

$\mu_{\bar X}= 83$

$\sigma_{\bar X}=\frac{27}{\sqrt{81}}= 3$

Part b

We want this probability:

$P(\bar X>89)$

We can use the z score formula given by:

$z = \frac{\bar X -\mu}{\frac{\sigma}{\sqrt{n}}}$

And if we find the z score for 89 we got:

$z= \frac{89-83}{\frac{27}{\sqrt{81}}}= 2$

$P(Z>2) = 1-P(Z$

Part c

$P(\bar X$

We can use the z score formula given by:

$z = \frac{\bar X -\mu}{\frac{\sigma}{\sqrt{n}}}$

And if we find the z score for 75.65 we got:

$z= \frac{75.65-83}{\frac{27}{\sqrt{81}}}= -2.45$

$P(Z$

Part d

We want this probability:

$P(79.4 < \bar X < 89.3)$

We find the z scores:

$z= \frac{89.3-83}{\frac{27}{\sqrt{81}}}= 2.1$

$z= \frac{79.4-83}{\frac{27}{\sqrt{81}}}= -1.2$

$P(-1.2$

8 0

3 years ago

A, B and C lie on a straight line.<br>Given that angle y = 135° and angle z = 97°, work out x.

Over [174]

Answer:

135°+97°+x=180°. 232°+x=180°. x=232-180=102°

:x=102°

8 0

3 years ago

How many feet are in 1 mile ?

strojnjashka [21]

There is 5280 feet in 1 mile.

hope this helps

4 0

3 years ago

Read 2 more answers

A license plate has a three-digit number printed on it. The product of the digits is 210, their sum is 18, and the numbers appea

tia_tia [17]

The answers are 7,6,5.

4 0

3 years ago

The average (arithmetic mean) of y numbers is x. If 30 is added to the set of numbers, then the average will be x − 5. What is t

Alenkasestr [34]

Answer:

y = $\frac{1}{5}(x^{2}-35x)$

Step-by-step explanation:

Let the total numbers are n.

If the average of y numbers is x then we can form an equation

$\frac{y}{n}=x$

⇒ $\frac{n}{y}=\frac{1}{x}$

⇒ n = $\frac{y}{x}$ --------(1)

Now 30 is added to the set of numbers then average becomes (x - 5)

$\frac{y+30}{n+1}=(x-5)$

⇒ $\frac{(n+1)}{(y+30)}=\frac{1}{(x-5)}$

⇒ (n + 1) = $\frac{y+30}{x-5}$

⇒ n = $\frac{y+30}{x-5}$ - 1 ----- (2)

Now we equate the values of n from equation 1 and 2

$\frac{y}{x}$ = $\frac{y+30}{x-5}$ - 1

y(x - 5) = x(y + 30) - x(x - 5) [ By cross multiplication ]

xy - 5y = xy + 30x - x² + 5x

xy - xy - 5y = 35x - x²

-5y = 35x - x²

x² - 35x = 5y

y = $\frac{1}{5}(x^{2}-35x)$

6 0

3 years ago

Read 2 more answers