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9.07 Further applications of the normal distribution

Interactive practice questions

The operating times of phone batteries are approximately normally distributed with mean $34$34 hours and a standard deviation of $4$4 hours. Answer the following questions using your calculator:

a

Approximately what percentage of batteries last between $33$33 and $38$38 hours?

Round your answer to the nearest percent.

b

Approximately what percentage of batteries last between $28$28 hours and $41$41 hours?

c

Any battery that lasts less than $23$23 hours is deemed faulty. If a company manufactured $51000$51000 batteries, approximately how many batteries would they be able to sell? Round your answer to the nearest integer.

Medium
1min

The height of sunflowers is approximately normally distributed, with a mean height of $1.6$1.6 m and a standard deviation of $8$8 cm.

Medium
1min

A machine is set for the production of cylinders of mean diameter $5.06$5.06 cm, with standard deviation $0.016$0.016 cm.

Medium
4min

A weather station records temperatures normally distributed with a mean of $28$28$^{\circ}$C and a standard deviation of $3.3$3.3$^{\circ}$C.

The temperatures were converted to Kelvin using the rule $Y=X+273.15$Y=X+273.15 where $X$X is the temperature in Celsius and $Y$Y is the temperature in Kelvin.

Easy
1min
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Outcomes

4.4.1.4

understand standardised normal variables (z-values, z-scores) and use these to compare samples

4.4.2.2

recognise features of the graph of the probability density function of the normal distribution with mean 𝜇 and standard deviation 𝜎 and the use of the standard normal distribution

4.4.2.3

calculate probabilities and quantiles associated with a given normal distribution using technology and use these to solve practical problems

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