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Weight ( $x$ kg) in class intervals	Frequency	Cumulative Frequency
$\phantom{30 \le}\; x \lt \color{red}{40}$	$0$	$\color{red}{0}$
$40 \le x \lt \color{red}{50}$	$10$	$\color{red}{10}$
$50 \le x \lt \color{red}{60}$	$18$	$\color{red}{28}$
$60 \le x \lt \color{red}{70}$	$13$	$\color{red}{41}$
$70 \le x \lt \color{red}{80}$	$15$	$\color{red}{56}$
$80 \le x \lt \color{red}{90}$	$4$	$\color{red}{60}$

Using this curve, we can also estimate the lower quartile (

$Q_1$ ), upper quartile (

$Q_3$ ) and hence the interquartile range.

If the median is the

$30$ th person's weight, the lower quartile (

$Q_1$ ) is the th person's weight and the upper quartile (

$Q_3$ ) is the th person's weight.

Find the following. Round answers to 3 significant figures.

$Q_1=$ kg

$Q_3=$ kg

Interquartile Range

$=$ kg

Estimate the number of people who weigh less than or equal to 56 kg.

people

Estimate the number of people who weigh more than or equal to 76 kg.

people

Round your answers to 3 significant figures.

The 50th percentile is the weight which 50% of the people are less than. The 50th percentile =

The 60th percentile is the weight which 60% of the people are less than. The 60th percentile =

The 90th percentile is the weight which 90% of the people are less than. The 90th percentile =

To estimate the standard deviation for continuous data, we use the mid-interval values as we did when estimating the mean.

Weight ( $x$ kg) in class intervals	Mid-interval Value	Frequency
$40 \le x \lt 50$	$45$	$10$
$50 \le x \lt 60$	$55$	$18$
$60 \le x \lt 70$	$65$	$13$
$70 \le x \lt 80$	$75$	$15$
$80 \le x \lt 90$	$85$	$4$

Using your Graphic Display Calculator, the standard deviation rounded to 3 significant figures is .