HARD
AS and A Level
IMPORTANT
Earn 100

Tomatoes from a certain producer have masses which are normally distributed with mean 90 grams and standard deviation 17.7 grams. The tomatoes are sorted into three categories by mass, as follows:
Small: under 80 g; Medium: 80 g to 104 g; Large: over 104 g.

Find, correct to 2 decimal places, the percentage of tomatoes in each of the three categories. Use ϕ0.565=0.71226, ϕ0.79=0.78524

Important Questions on The Normal Distribution

HARD
AS and A Level
IMPORTANT

Tomatoes from a certain producer have masses which are normally distributed with mean 90 grams and standard deviation 17.7 grams. The tomatoes are sorted into three categories by mass, as follows:
Small: under 80 g; Medium: 80 g to 104 g; Large: over 104 g.

Find the value of k such that P(kX<104)=0.75, where X is the mass of a tomato in grams. Use ϕ0.79=0.78524, ϕ-10.0352=-1.805

HARD
AS and A Level
IMPORTANT
The heights, in metres, of the trees in a forest are normally distributed with mean μ and standard deviation 3.6. Given that 75% of the trees are less than 10 m high, find the value of μ. Use ϕ-10.75=0.674
HARD
AS and A Level
IMPORTANT

The mass of a certain species of fish caught at sea is normally distributed with mean 5.73 kg and variance 2.56 kg2. Find the probability that a randomly selected fish caught at sea has a mass that is: less than 6.0 kg. Use ϕ0.169=0.567

HARD
AS and A Level
IMPORTANT

The mass of a certain species of fish caught at sea is normally distributed with mean 5.73 kg and variance 2.56 kg2. Find the probability that a randomly selected fish caught at sea has a mass that is: more than 3.9 kg. Use ϕ1.144=0.874

HARD
AS and A Level
IMPORTANT

The mass of a certain species of fish caught at sea is normally distributed with mean 5.73 kg and variance 2.56 kg2. Find the probability that a randomly selected fish caught at sea has a mass that is: between 7.0kg and 8.0kg. Use ϕ1.149=0.92220, ϕ0.794=0.788

HARD
AS and A Level
IMPORTANT

The distance that children at a large school can hop in 15 minutes is normally distributed with mean 199 m and variance 3700 m2.

Calculate an estimate of b, given that only 25% of the children hopped further than b metres. Use ϕ-10.75=0.674

HARD
AS and A Level
IMPORTANT

The distance that children at a large school can hop in 15 minutes is normally distributed with mean 199 m and variance 3700 m2.

Calculate an estimate of b, given that only 25% of the children hopped further than b metres. Find an estimate of the interquartile range of the distances hopped. Use ϕ-10.75=0.674

HARD
AS and A Level
IMPORTANT
The daily percentage change in the value of a company's shares is expected to be normally distributed with mean 0 and standard deviation 0.51. On how many of the next 365 working days should the company expect the value of its shares to fall by more than 1%? [ Use Φ(1.961)=0.9751]