Skip to content
MathsGenie logo
Quick links
Open app

Course home

  1. A Level
  3. Maths OCR (MEI)
  5. Question bank

2.4.12 Calculate probabilities from a Normal distribution (A-level only)

EasyMediumHard
1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859606162636465666768697071
Question 36

The lifetime of Lumos LED bulbs, XXX units of hours, is normally distributed with mean 12,000 hours and standard deviation 800 hours.

ai.

Find P(X≠12000)P(X \neq 12000)P(X=12000).

[1]
aii.

Find P(11000<X<13500)P(11000 < X < 13500)P(11000<X<13500).

[3]
b.

Determine the lifetime exceeded by 80% of Lumos LED bulbs.

[3]
c.

A different brand, Glow, has its bulb lifetime, YYY hours, modelled by a normal distribution with mean 11,000 hours and standard deviation σ\sigmaσ. Given that 15% of randomly selected Glow bulbs last less than 9,500 hours, find the value of σ\sigmaσ, correct to three significant figures.

[3]

2.4.12 Calculate probabilities from a Normal distribution (A-level only) Questions

  1. A Level
  2. /Maths
  3. /2.4.12 Calculate probabilities from a Normal distribution (A-level only)