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Answer:
a) 68.26% probability that a student scores between 350 and 550
b) A score of 638(or higher).
c) The 60th percentile of test scores is 475.3.
d) The middle 30% of the test scores is between 411.5 and 488.5.
Step-by-step explanation:
Problems of normally distributed samples are solved using the z-score formula.
In a set with mean and standard deviation
, the zscore of a measure X is given by:
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.
In this problem, we have that:
a. What is the probability that a student scores between 350 and 550?
This is the pvalue of Z when X = 550 subtracted by the pvalue of Z when X = 350. So
X = 550
has a pvalue of 0.8413
X = 350
has a pvalue of 0.1587
0.8413 - 0.1587 = 0.6826
68.26% probability that a student scores between 350 and 550
b. If the upper 3% scholarship, what score must a student receive to get a scholarship?
100 - 3 = 97th percentile, which is X when Z has a pvalue of 0.97. So it is X when Z = 1.88
A score of 638(or higher).
c. Find the 60th percentile of the test scores.
X when Z has a pvalue of 0.60. So it is X when Z = 0.253
The 60th percentile of test scores is 475.3.
d. Find the middle 30% of the test scores.
50 - (30/2) = 35th percentile
50 + (30/2) = 65th percentile.
35th percentile:
X when Z has a pvalue of 0.35. So X when Z = -0.385.
65th percentile:
X when Z has a pvalue of 0.35. So X when Z = 0.385.
The middle 30% of the test scores is between 411.5 and 488.5.
Considering the definition of perpendicular line, the equation of of perpendicular line is y= -x +
.
A linear equation o line can be expressed in the form y = mx + b.
where
x and y are coordinates of a point.
m is the slope.
b is the ordinate to the origin and represents the coordinate of the point where the line crosses the y axis.
<h3>Perpendicular line</h3>Perpendicular lines are lines that intersect at right angles or 90° angles. If you multiply the slopes of two perpendicular lines, you get –1.
<h3>Equation of perpendicular line in this case</h3>In this case, the line is 2x-y=8. Expressed in the form y = mx + b, you get:
-y=8 - 2x
y= (-2x +8)÷ (-1)
y= 2x -8
If you multiply the slopes of two perpendicular lines, you get –1. In this case, the line has a slope of 2. So:
2× slope perpendicular line= -1
slope perpendicular line= (-1)÷ (2)
<u><em>slope perpendicular line= -</em></u>
So, the perpendicular line has a form of: y= -x + b
The line passes through the point (9, 2). Replacing in the expression for perpendicular line:
2= (-)× 9 + b
2= - + b
2+ = b
<u><em /></u><u><em>= b</em></u>
Finally, the equation of of perpendicular line is y= -x +
.
Learn more about perpendicular line:
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