Skip to content

Course home

3.2 Finding Probabilities for Normal Distributions

3.2 Finding Probabilities for Normal Distributions

EasyMediumHard
12345678910111213141516171819202122232425262728293031323334353637383940414243444546474849505152
Question 20

A high-precision industrial sensor measures the deviation of a mechanical component's width from a target value. The deviation, DDD microns, follows a normal distribution with a mean of 82 μm82\ \mu\text{m}82 μm and a standard deviation of 6.0 μm6.0\ \mu\text{m}6.0 μm.

a.

Find the probability that a component selected at random has a deviation greater than 95 μm95\ \mu\text{m}95 μm.

[3]
b.

The machine is recalibrated so that the mean deviation is μ\muμ but the standard deviation remains at 6.0 μm6.0\ \mu\text{m}6.0 μm. Two independent components are measured by the sensor.

The probability that both components have a deviation of less than 75 μm75\ \mu\text{m}75 μm is 0.160.160.16.

Calculate the value of μ\muμ, giving your answer to 1 decimal place.

[4]
c.

A different calibration is tested where the mean deviation is 151515 and the standard deviation is 202020.

The sensor then records 5 independent readings from this distribution.

Determine the probability that the deviation is negative for at least one of these components.

[4]
Markscheme

3.2 Finding Probabilities for Normal Distributions Questions

  1. A Level
  2. /Maths
  3. /3.2 Finding Probabilities for Normal Distributions

80 exam-style questions on Edexcel A Level Maths 3.2 Finding Probabilities for Normal Distributions. Each one has a worked solution and a mark scheme showing where the marks go.

Question bank