Joanna split 3 pitchers of water equally among her 8 plants. What fraction of a pitcher did each plant get?

For a particular diamond mine, 81% of the diamonds fail to qualify as "gemstone grade". A random sample of 92 diamonds is analyz

Fed [463]

Answer:

68.79% probability that more than 79% of the sample diamonds fail to qualify as gemstone grade

Step-by-step explanation:

We use the binomial approximation to the normal to solve this question.

Binomial probability distribution

Probability of exactly x sucesses on n repeated trials, with p probability.

Can be approximated to a normal distribution, using the expected value and the standard deviation.

The expected value of the binomial distribution is:

$E(X) = np$

The standard deviation of the binomial distribution is:

$\sqrt{V(X)} = \sqrt{np(1-p)}$

Normal probability distribution

Problems of normally distributed samples can be 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.

When we are approximating a binomial distribution to a normal one, we have that $\mu = E(X)$ , $\sigma = \sqrt{V(X)}$ .

In this problem, we have that:

$n = 92, p = 0.81$

So

$\mu = E(X) = np = 92*0.81 = 74.52$

$\sigma = \sqrt{V(X)} = \sqrt{np(1-p)} = \sqrt{92*0.81*0.19} = 3.76$

Find the probability that more than 79% of the sample diamonds fail to qualify as gemstone grade.

This is 1 subtracted by the pvalue of Z when X = 0.79*92 = 72.68. So

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

$Z = \frac{72.68 - 74.52}{3.76}$

$Z = -0.49$

$Z = -0.49$ has a pvalue of 0.3121

1 - 0.3121 = 0.6879

68.79% probability that more than 79% of the sample diamonds fail to qualify as gemstone grade

4 0

3 years ago

A chord of a circle is 66cm long, it is 56 cm from the center of the circle. What is the radius of the circle?

ser-zykov [4K]

Answer:

radius = 65 cm

Step-by-step explanation:

(See image attached for better comprehension)

To find the value of the radius, we just need to draw a triangle, where one side is half of the chord (the distance from the chord to the center creates a point that divides the chord in two equal segments), other side is the distance from the chord to the center, and the hypotenusa will be the radius.

So, using Pythagoras' theorem, we have that:

r^2 = 56^2 + 33^2

r^2 = 4225

r = 65 cm