Two thirds x one fourth .

Rockwell hardness of pins of a certain type is known to have a mean value of 50 and a standard deviation of 1.8. (Round your ans

Alenkinab [10]

Answer:

a) 0.011 = 1.1% probability that the sample mean hardness for a random sample of 17 pins is at least 51

b) 0.0001 = 0.1% probability that the sample mean hardness for a random sample of 45 pins is at least 51

Step-by-step explanation:

To solve this question, we need to understand the normal probability distribution and the central limit theorem.

Normal probability distribution

Problems of normally distributed samples are solved using the z-score formula.

In a set with mean $\mu$ and standard deviation $\sigma$ , the zscore of a measure X is given by:

$Z = \frac{X - \mu}{\sigma}$

The Z-score measures how many standard deviations the measure is from the mean. After finding the Z-score, we look at the z-score table and find the p-value 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. Subtracting 1 by the pvalue, we get the probability that the value of the measure is greater than X.

Central Limit Theorem

The Central Limit Theorem estabilishes that, for a normally distributed random variable X, with mean $\mu$ and standard deviation $\sigma$ , the sampling distribution of the sample means with size n can be approximated to a normal distribution with mean $\mu$ and standard deviation $s = \frac{\sigma}{\sqrt{n}}$ .

For a skewed variable, the Central Limit Theorem can also be applied, as long as n is at least 30.

In this problem, we have that:

$\mu = 50, \sigma = 1.8$

(a) If the distribution is normal, what is the probability that the sample mean hardness for a random sample of 17 pins is at least 51?

Here $n = 17, s = \frac{1.8}{\sqrt{17}} = 0.4366$

This probability is 1 subtracted by the pvalue of Z when X = 51. So

$Z = \frac{X - \mu}{\sigma}$

By the Central Limit Theorem

$Z = \frac{X - \mu}{s}$

$Z = \frac{51 - 50}{0.4366}$

$Z = 2.29$

$Z = 2.29$ has a pvalue of 0.9890

1 - 0.989 = 0.011

0.011 = 1.1% probability that the sample mean hardness for a random sample of 17 pins is at least 51

(b) What is the (approximate) probability that the sample mean hardness for a random sample of 45 pins is at least 51?

Here $n = 17, s = \frac{1.8}{\sqrt{45}} = 0.2683$

$Z = \frac{X - \mu}{s}$

$Z = \frac{51 - 50}{0.0.2683}$

$Z = 3.73$

$Z = 3.73$ has a pvalue of 0.9999

1 - 0.9999 = 0.0001

0.0001 = 0.1% probability that the sample mean hardness for a random sample of 45 pins is at least 51

8 0

3 years ago

At a wedding, there are 456 people spread out amongst 45 tables. There are no empty seats. The reception hall has tables that si

uysha [10]

Thats a lot of people for one resturant

3 0

3 years ago

Can someone help me? After I figure out the sequence i have to write the formula. please help.

sveta [45]

Rewrite the fractions to have a common denominator to find the difference:

2/3 = 4/6

Difference = 4/6-5/6 = -1/6

Sequence formula = an = a1 + d(n-1)

A1 is the first term 5/6

And d = -1/6

Sequence = 5/6 -1/6(n-1)

Simplify to get an =(-n +6)/6

3 0

3 years ago

Consider the quadratic equation ax^2+bx+5=0,where a, b and c are rational numbers and the quadratic has two distinct zeros.

FrozenT [24]

You have shared the situation (problem), except for the directions: What are you supposed to do here? I can only make a educated guesses. See below:

Note that if   <span>ax^2+bx+5=0 then it appears that c = 5 (a rational number).

Note that for simplicity's sake, we need to assume that the "two distinct zeros" are real numbers, not imaginary or complex numbers. If this is the case, then the discriminant, b^2 - 4(a)(c), must be positive. Since c = 5,

b^2 - 4(a)(5) > 0, or b^2 - 20a > 0.

Note that if the quadratic has two distinct zeros, which we'll call "d" and "e," then

(x-d) and (x-e) are factors of ax^2 + bx + 5 = 0, and that because of this fact,

- b plus sqrt( b^2 - 20a )
d =  ------------------------------------
2a

and

</span> - b minus sqrt( b^2 - 20a )
e =  ------------------------------------
2a

Some (or perhaps all) of these facts may help us find the values of "a" and "b." Before going into that, however, I'm asking you to share the rest of the problem statement. What, specificallyi, were you asked to do here?

7 0

3 years ago

Part B: Give an example of an undefined term and how it relates to a circle. (5 points)

ivann1987 [24]

Answer:

hello

Step-by-step explanation:

hello

5 0

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