Mathematics, 19.02.2021 03:10 Jwhite8602

Find the z-score boundaries that separate a normal distribution as described in each of the following. a. The middle 20% from the 80% in the tails. b. The middle 50% from the 50% in the tails. c. The middle 95% from the 5% in the tails. d. The middle 99% from the 1% in the tails.

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Answer from: emilylittle2442

a) The boundaries are $Z = \pm 0.253$

b) The boundaries are $Z = \pm 0.675$ .

c) The boundaries are $Z = \pm 1.96$ .

d) The boundaries are $Z = \pm 2.575$ .

Step-by-step explanation:

Z-score:

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.

a. The middle 20% from the 80% in the tails.

The middle 20% is between the 50 - (20/2) = 40th percentile and the 50 + (20/2) = 60th percentile:

40th percentile: Z has a pvalue of 0.4, so Z = -0.253.

60th percentile: Z has a pvalue of 0.6, so Z = 0.253.

The boundaries are $Z = \pm 0.253$ .

b. The middle 50% from the 50% in the tails.

The middle 50% is between the 50 - (50/2) = 25th percentile and the 50 + (50/2) = 75th percentile:

25th percentile: Z has a pvalue of 0.25, so Z = -0.675.

75th percentile: Z has a pvalue of 0.75, so Z = 0.675.

The boundaries are $Z = \pm 0.675$ .

c. The middle 95% from the 5% in the tails.

The middle 95% is between the 50 - (95/2) = 2.5th percentile and the 50 + (95/2) = 97.5th percentile:

2.5th percentile: Z has a pvalue of 0.025, so Z = -1.96.

97.5th percentile: Z has a pvalue of 0.975, so Z = 1.96.

The boundaries are $Z = \pm 1.96$ .

d. The middle 99% from the 1% in the tails.

The middle 99% is between the 50 - (99/2) = 0.5th percentile and the 50 + (99/2) = 99.5th percentile:

0.5th percentile: Z has a pvalue of 0.005, so Z = -2.575.

99.5th percentile: Z has a pvalue of 0.995, so Z = 2.575.

The boundaries are $Z = \pm 2.575$ .

Answer from: Quest

solution:

the given function is ,

$f(x) = 4 x^3 - 72 x^2 + 320 x,$

= $4x( x^2- 18 x + 80)\\\\ 4 x(x^2-10 x -8 x + 80) \\\\ 4 x[(x-10)(x-8)]$

the three roots of this quadratic function is , 0 ,8 and 10.all the roots are real and rational.

if a quadratic equation is of the form ,

$f(x) = a x^3+ b x^2 + c x+d,$

sum of the roots = a + b +c= 0+8+10=18= $\frac{-b}{a}$

product of roots taken two at a time = a b + b c+ c a = 0+80+0=80 = $\frac{c}{a}$

product of roots = a b c = 0= $\frac{d}{a}$

there are 11 doors in a hall starting from 0 to 11.the entry in the hall is permitted through gate number 0 and exit is allowed through only gate number 8 and 10.so, three roots(0,8,10) of quadratic function $f(x) = 4 x^3 - 72 x^2 + 320 x,$ is given by entry and exit route of this hall.

Answer from: Quest

Could you make it more clear?
This is ! be right about ur ! ! both questions and u

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