Population = 135 students
Mean score = 72.3
Standard deviation of the scores = 6.5
Part (a): Students from 2SD and 3SD above the mean
2SD below and above the mean includes 95% of the population while 3SD includes 99.7% of the population.
95% of population = 0.95*135 ≈ 129 students
99.7% of population = 0.997*135 ≈ 135 students
Therefore, number of students from 2SD to 3SD above and below the bean = 135 - 129 = 6 students.
In this regard, Students between 2SD and 3SD above the mean = 6/2 = 3 students
Part (b): Students who scored between 65.8 and 72.3
The first step is to calculate Z values
That is,
Z = (mean-X)/SD
Z at 65.8 = (72.3-65.8)/6.5 = 1
Z at 72.3 = (72.3-72.3)/6.5 = 0
Second step is to find the percentages at the Z values from Z table.
That is,
Percentage of population at Z(65.8) = 0.8413 = 84.13%
Percentage of population at (Z(72.3) = 0.5 = 50%
Third step is to calculate number of students at each percentage.
That is,
At 84.13%, number of students = 0.8413*135 ≈ 114
At 50%, number of students = 0.5*135 ≈ 68
Therefore, students who scored between 65.8 and 72.3 = 114-68 = 46 students
If the radius of the circle is 6 feet. Then the area of the circle will be 113.097 square feet.
<h3>What is a circle?</h3>
It is the centre of an equidistant point drawn from the centre. The radius of a circle is the distance between the centre and the circumference.
The radius of the circle is 6 feet.
Then the area of the circle will be
Area = πr²
where r is the radius of the circle. Then we have
Area = π × 6²
Area = 36π
Area = 113.097 square feet
More about the circle link is given below.
brainly.com/question/11833983
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C)
10hrs will get around 105 salaries
90hrs get 840+105=945
95 hours get 945+(105/2)=997.5
100 hours get 945+105=1050
