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1 year ago

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in a significance test of one population mean if vairance of population is unknown but the sample size is 30 or more we use z te

st why?

1 answer:

Talja [164]1 year ago

4 0

The student T distribution would be used since we don't know the population variance (by extension the population standard deviation).

However, if n > 30, then the student T distribution is going to look very similar to the standard normal Z distribution. It won't be a perfect match, but it'll be close enough that it's more simple to use the Z distribution. With the Z distribution, you only have one set of values and you don't have to worry about the degrees of freedom.

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Amanda invests 5000 in a cd at an annual rate of 2%. What will her investment be worth at the end of three years?

Nookie1986 [14]

The equations would be 5000(1+0.02)^3 and the answer is $5306.04

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2 years ago

Read 2 more answers

A 13?-foot board is cut into two pieces. The longer piece is 7.5 feet longer than the shorter piece. What is the length of each?

chubhunter [2.5K]

Answer:

The smaller board would be 2.75 feet and the longer one would be 10.25 feet.

Step-by-step explanation:

In order to find this, assume the shorter board is equal to x. Next, we would know that the longer board would be equal to x + 7.5. Using these two assumptions, we can add the lengths together, set equal to 13 and then solve for x.

x + (x + 7.5) = 13

2x + 7.5 = 13

2x = 5.5

x = 2.75

Now that we have the length of the shorter board, we can add 7.5 to it to get the larger one.

2.75 + 7.5 = 10.25

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3 years ago

Oil is pumped continuously from a well at a rate proportional to the amount of oil left in the well. Initially there were millio

JulijaS [17]

Answer:

The amount of oil was decreasing at 69300 barrels, yearly

Step-by-step explanation:

Given

$Initial =1\ million$

$6\ years\ later = 500,000$

Required

At what rate did oil decrease when 600000 barrels remain

To do this, we make use of the following notations

t = Time

A = Amount left in the well

So:

$\frac{dA}{dt} = kA$

Where k represents the constant of proportionality

$\frac{dA}{dt} = kA$

Multiply both sides by dt/A

$\frac{dA}{dt} * \frac{dt}{A} = kA * \frac{dt}{A}$

$\frac{dA}{A} = k\ dt$

Integrate both sides

$\int\ {\frac{dA}{A} = \int\ {k\ dt}$

$ln\ A = kt + lnC$

Make A, the subject

$A = Ce^{kt}$

$t = 0\ when\ A =1\ million$ i.e. At initial

So, we have:

$A = Ce^{kt}$

$1000000 = Ce^{k*0}$

$1000000 = Ce^{0}$

$1000000 = C*1$

$1000000 = C$

$C =1000000$

Substitute $C =1000000$ in $A = Ce^{kt}$

$A = 1000000e^{kt}$

To solve for k;

$6\ years\ later = 500,000$

i.e.

$t = 6\ A = 500000$

So:

$500000= 1000000e^{k*6}$

Divide both sides by 1000000

$0.5= e^{k*6}$

Take natural logarithm (ln) of both sides

$ln(0.5) = ln(e^{k*6})$

$ln(0.5) = k*6$

Solve for k

$k = \frac{ln(0.5)}{6}$

$k = \frac{-0.693}{6}$

$k = -0.1155$

Recall that:

$\frac{dA}{dt} = kA$

Where

$\frac{dA}{dt}$ = Rate

So, when

$A = 600000$

The rate is:

$\frac{dA}{dt} = -0.1155 * 600000$

$\frac{dA}{dt} = -69300$

<em>Hence, the amount of oil was decreasing at 69300 barrels, yearly</em>

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2 years ago

I will mark branliest for ever Andrews first and it’s also 40 points

navik [9.2K]

Answer:

see below

Step-by-step explanation:

5/10 divide ?/?= 1/2

5/10 divide by 5/5 = 1/2

2. 12/15 divide ?/? = 4/5

12/15 divide by 3/3 = 4/5

3. 10/12divide ?/? = 5/6

10/12 divide by 2/2 = 5/6

4. 14/18 divide ?/? = 7/9

14/18 divide by 2/2 = 7/9

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2 years ago

The surface area of a ball is 3,600 square millimeters. What is the balls radius

allsm [11]

$A = 4 \pi r^2$

$3600 = 4\pi r^2$

$\dfrac{3600}{4 \pi} = r^2$

$r^2 = 286.479$

$r = 16.9$

Answer: The radius is 16.9 mm.

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3 years ago