A large group of students took a test in Physics and the final grades have a mea

Question

A large group of students took a test in Physics and the final grades have a mean of 80 and a standard deviation of 7. 97.98% of the students received a score on the test that was greater than what grade? (round to nearest whole number)

A radar unit is used to measure speeds of cars on a motorway. The speeds are normally distributed with a mean of 90 km/hr and a standard deviation of 10 km/hr. What is the measured speed that is 2.34 standard deviations below the mean o 90 km/hr? (round to tenths place)

Explanation / Answer

a)

mean = 80

standard deviation = 7.97

let us assume that 98% of the students received a score on the test that was greater than H

i.e P(X>H) = 0.98 => P(X<H) = 0.02

z value for H is (H-80)/7.97 which is equal to z value for p=0.02

using z table z value for 0.02 is -2.054

(H-80)/7.97 = -2.054

H = 80-7.97*2.054 = 63.629 ~ 64

98% of the students received a score on the test that was greater than 64

b)

mean = 90

standard deviation = 10

let measured speed that is 2.34 standard deviations below the mean o 90 km/hr be S

=> S = 90-2.34*10 = 66.6

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.